O gives you a useful mix of everyday adjectives and more precise descriptive words. Familiar choices such as old, open, odd, ordinary, and original work in many situations, while words such as observant, obstinate, ornate, ominous, and opulent express more specific qualities.
You can use O adjectives to describe people, appearance, shapes, places, feelings, conditions, and situations. The quick list below gives you short meanings, followed by examples and useful word distinctions.
Adjectives That Start With O: Quick List
| Adjective | Meaning |
|---|---|
| Oafish | Clumsy or lacking good manners |
| Obdurate | Stubbornly refusing to change |
| Obedient | Willing to follow rules or instructions |
| Objective | Based on facts rather than personal feelings |
| Objectionable | Unpleasant or likely to cause disapproval |
| Obligatory | Required by a rule, law, or custom |
| Obliging | Willing and ready to help |
| Oblique | Slanting rather than straight; indirect |
| Oblivious | Unaware of what is happening |
| Oblong | Longer than it is wide |
| Obnoxious | Extremely unpleasant or annoying |
| Obscure | Difficult to understand or not well known |
| Observant | Good at noticing details |
| Obsessive | Excessively focused on one idea or activity |
| Obsolete | No longer used because something newer has replaced it |
| Obsequious | Excessively eager to please or obey |
| Obstinate | Stubbornly refusing to change |
| Obstructive | Making progress or movement difficult |
| Obtainable | Possible to get or achieve |
| Obtrusive | Noticeable in an unwanted or intrusive way |
| Obtuse | Slow to understand; also greater than 90° and less than 180° in geometry |
| Obvious | Easy to notice or understand |
| Occasional | Happening from time to time |
| Occupational | Relating to a job or profession |
| Occupied | Being used or already taken |
| Oceanic | Relating to the ocean |
| Odd | Strange, unusual, or not expected |
| Odd-looking | Unusual in appearance |
| Odorless | Having no noticeable smell |
| Offbeat | Unusual or unconventional |
| Offensive | Insulting, unpleasant, or causing offense |
| Official | Approved or authorized |
| Oily | Containing, covered with, or resembling oil |
| Old | Having existed or lived for a long time |
| Old-fashioned | Belonging to or typical of an earlier time |
| Ominous | Suggesting that something bad may happen |
| Omnivorous | Eating both plants and animals |
| Ongoing | Continuing at the present time |
| Online | Connected with or available through the internet |
| Open | Not closed; also willing to consider ideas |
| Open-ended | Having no fixed limit or predetermined conclusion |
| Open-minded | Willing to consider different ideas |
| Operational | Ready for use or functioning |
| Opportune | Happening at a suitable or convenient time |
| Optimistic | Expecting good results |
| Optimal | Best or most favorable |
| Optional | Available by choice rather than required |
| Orange | Having the color orange |
| Orderly | Neat, organized, or well behaved |
| Ordinary | Normal or not unusual |
| Organic | Relating to living things; also used for food or farming produced according to organic standards |
| Original | New, creative, or existing from the beginning |
| Ornamental | Intended mainly for decoration |
| Ornate | Highly decorated |
| Ornery | Bad-tempered or difficult; informal, especially American English |
| Orthodox | Following traditional or generally accepted ideas |
| Ostensible | Appearing or claimed to be true, though it may not be the real explanation |
| Ostentatious | Designed to attract attention or display wealth |
| Outdoor | Intended for or happening outside |
| Outdoorsy | Fond of outdoor activities; informal |
| Outgoing | Friendly and comfortable with other people |
| Outlandish | Very strange or unconventional |
| Outlying | Situated far from the center |
| Outrageous | Shockingly unreasonable, offensive, or excessive |
| Outraged | Extremely angry or offended |
| Outspoken | Expressing opinions openly and directly |
| Outstanding | Exceptionally good or noticeable |
| Oval | Having a rounded, egg-like shape |
| Overall | Considering everything together |
| Overactive | Excessively active |
| Overbearing | Too controlling or domineering |
| Overcast | Covered with clouds |
| Overconfident | More confident than is reasonable |
| Overcrowded | Containing too many people or things |
| Overdue | Not done, paid, or returned by the expected time |
| Overgrown | Covered with excessive plant growth |
| Overjoyed | Extremely happy |
| Opulent | Extremely luxurious or richly decorated |
| Oversized | Larger than the usual or standard size |
| Overwhelmed | Feeling unable to cope because too much is happening |
| Overwhelming | Extremely powerful, intense, or difficult to manage |
Common O Adjectives in Everyday English
Some O adjectives appear regularly because they can describe many different people, things, and situations.
Obvious
Obvious describes something that is easy to notice, recognize, or understand.
The answer became obvious once Mia saw the diagram.
Occasional
Occasional means happening sometimes rather than regularly.
We get occasional thunderstorms during the summer.
Odd
Odd often means strange, unusual, or unexpected.
There was an odd noise coming from the attic.
It can also have mathematical meanings, as in an odd number.
Old
Old describes someone or something that has existed for a relatively long time.
An old stone bridge crosses the river.
Its exact meaning depends on what is being described. A five-year-old phone may be considered old, while a five-year-old tree usually would not.
Ordinary
Ordinary means normal, usual, or not particularly unusual.
It looked like an ordinary wooden box.
Original
Original can describe something that is new or creatively different.
Sofia presented an original solution to the problem.
It can also mean the first version of something.
The museum still has the original manuscript.
Outstanding
Outstanding often means exceptionally good.
Priya did outstanding work on the project.
It can also mean unresolved or not yet completed.
We still have several outstanding issues to discuss.
O Adjectives to Describe a Person
O has several useful adjectives for personality, behavior, attitude, and social style.
Obedient
Obedient describes someone who follows rules, instructions, or the commands of another person.
The obedient child followed the safety instructions carefully.
When used for people, the word is most natural in contexts involving authority, rules, or expected behavior.
Obliging
An obliging person is willing to help or accommodate others.
The obliging receptionist found us a quieter room.
Obnoxious
Obnoxious describes someone or something extremely unpleasant or annoying.
His obnoxious behavior ruined the conversation for everyone else.
Obstinate
An obstinate person stubbornly refuses to change their opinion or behavior.
The obstinate customer would not consider any alternative.
Orderly
When describing behavior, orderly means organized, controlled, or well behaved.
The crowd remained calm and orderly.
Optimistic
An optimistic person expects good things to happen or believes a situation will improve.
Nina remained optimistic despite the disappointing first results.
Ornery
Ornery is an informal adjective meaning bad-tempered, difficult, or stubborn.
The ornery customer complained about every small detail.
The word is especially common in American English.
Outdoorsy
An outdoorsy person enjoys activities such as hiking, camping, fishing, or spending time outside.
Luis is outdoorsy and spends most weekends hiking.
Outgoing
An outgoing person is sociable, friendly, and comfortable meeting others.
Her outgoing personality made it easy for her to make new friends.
Outspoken
An outspoken person expresses opinions openly and directly.
Carla has been outspoken about the need for better public transportation.
Being outspoken does not necessarily mean being rude. It mainly suggests a willingness to state opinions clearly.
Overbearing
Overbearing describes someone who tries to control other people too strongly.
His overbearing management style frustrated the team.
Overconfident
An overconfident person has more confidence than the situation justifies.
The overconfident player underestimated his opponent.
O Adjectives for Appearance, Shape, and Physical Condition
Oblong
Oblong describes a shape that is longer than it is wide.
The dining table has an oblong top.
Odd-looking
Odd-looking describes someone or something with an unusual appearance.
An odd-looking mushroom was growing beside the path.
Oily
Oily means containing, covered with, or resembling oil.
The mechanic wiped his oily hands on a cloth.
It can also describe food with more oil than someone finds pleasant.
The noodles were heavy and oily.
Orange
Orange describes the color between red and yellow.
She carried a bright orange umbrella.
Ornamental
Ornamental describes something mainly intended to make a place or object more attractive.
Ornamental trees line the entrance to the garden.
Ornate
Ornate describes something decorated with many elaborate details.
The building has an ornate stone entrance.
Oval
Oval describes a rounded shape that is longer in one direction than the other.
The mirror has an oval frame.
Oversized
Oversized describes something larger than the usual or standard size.
Ben wore an oversized sweater on the flight.
O Adjectives for Places, Nature, and Surroundings
Oceanic
Oceanic means relating to the ocean.
The island has a warm oceanic climate.
Outdoor
Outdoor describes something that happens, exists, or is intended for use outside.
The hotel has an outdoor swimming pool.
Outlying
Outlying describes a place situated some distance from a central area.
Medical teams traveled to several outlying villages.
Overcast
Overcast describes a sky covered with clouds.
The morning was cool and overcast.
Overcrowded
Overcrowded describes a place containing more people or things than it can comfortably handle.
The train became overcrowded during rush hour.
Overgrown
Overgrown describes an area covered with plants that have grown too much or without control.
An overgrown path led toward the abandoned cottage.
O Adjectives for Feelings, Experiences, and Situations
Ominous
Ominous describes something that suggests trouble or danger may be coming.
Dark clouds gathered in an ominous sky.
Opportune
Opportune describes something happening at a particularly suitable or convenient time.
The announcement came at an opportune moment.
Outrageous
Outrageous can describe something shockingly unreasonable, offensive, or excessive.
The hotel charged an outrageous price for a small room.
In informal speech, it can sometimes be used positively for something unusually impressive, but the negative sense is more common.
Overdue
Overdue describes something that should already have happened, been completed, paid, or returned.
The library book is three weeks overdue.
It is also common in expressions such as:
The repairs are long overdue.
Overjoyed
Overjoyed means extremely happy.
Mia was overjoyed when she heard the news.
Outraged
Outraged describes someone who feels extremely angry or offended.
Residents were outraged by the sudden decision.
Observant or Oblivious?
Observant and oblivious describe almost opposite ways of noticing what is happening around you.
An observant person notices details easily.
The observant detective spotted a mark on the window frame.
An oblivious person is unaware of something happening nearby or fails to notice it.
Ryan was oblivious to the conversation behind him.
So:
- observant = quick to notice
- oblivious = unaware or not noticing
Overwhelmed or Overwhelming?
These two adjectives are closely related, but they describe different sides of an experience.
Overwhelmed describes the person experiencing a very strong feeling or too much pressure.
I felt overwhelmed by the amount of work waiting for me.
Overwhelming describes the thing, feeling, or situation that creates that powerful effect.
The amount of information was overwhelming.
Compare:
The new employee felt overwhelmed.
The first week was overwhelming.
The same distinction appears in adjective pairs such as bored/boring and interested/interesting.
Open or Open-Minded?
Open has many meanings, including not closed and willing to consider something.
Maya is open to suggestions.
Open-minded is more specific. It describes someone willing to consider unfamiliar ideas or opinions without rejecting them immediately.
A good discussion requires people to remain open-minded.
Someone can therefore be open to one particular suggestion, while being open-minded describes a broader attitude toward ideas and viewpoints.
Less Common O Adjectives Worth Knowing
Obdurate
Obdurate is a formal adjective meaning stubbornly refusing to change an opinion or course of action.
The committee remained obdurate despite growing criticism.
Obsequious
Obsequious describes someone who is excessively eager to please or obey another person, often because they hope to gain an advantage.
The manager disliked the employee’s obsequious manner.
Obtrusive
Obtrusive describes something that attracts unwanted attention or intrudes noticeably.
The large security camera looked obtrusive in the small room.
Obtuse
When describing a person, obtuse can mean slow to understand something that seems clear to others.
He was being deliberately obtuse about the point she was making.
In geometry, an obtuse angle measures more than 90 degrees but less than 180 degrees.
Opulent
Opulent describes something extremely luxurious or richly decorated.
The palace contains several opulent reception rooms.
Ostensible
Ostensible describes a reason, purpose, or situation that appears or is claimed to be true, although the real explanation may be different.
The ostensible purpose of the visit was to discuss trade.
Ostentatious
Ostentatious describes something deliberately showy, often because someone wants to display wealth or importance.
He arrived in an ostentatious car covered with flashy details.
Orthodox
Orthodox describes beliefs, methods, or practices that follow established or traditional ideas.
Her proposal challenged the orthodox view of the issue.
For adjectives beginning with every letter of the alphabet, see the A–Z list of adjectives with meanings.
Explore Adjectives by Letter
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N | O | P | Q | R | S | T | U | V | W | X | Y | Z
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