Adjectives That Start With O

Obdurate: Stubbornly refusing to change one's opinion or course of action.

Obedient: Willing to comply with orders or requests.

Obese: Extremely overweight.

Obligate: Required or compulsory.

Obligatory: Required by a legal, moral, or other rule; compulsory.

Obliging: Willing to do a service or kindness; helpful.

Oblique: Not straightforward or direct; indirect.

Obliterated: Destroyed completely.

Oblivious: Not aware of or not concerned about what is happening around one.

Oblong: Having an elongated shape.

Obnoxious: Extremely unpleasant.

Obscene: Offensive or disgusting by accepted standards of morality and decency.

Obscure: Not clearly expressed or easily understood.

Obscured: Hidden or made less visible.

Obsequious: Excessively obedient or attentive to an ingratiating degree.

Observant: Quick to notice or perceive things.

Observational: Relating to the action or process of closely observing or monitoring something.

Obsessive: Excessive and compulsive.

Obsolescent: Becoming obsolete.

Obsolete: No longer produced or used; out of date.

Obstinate: Stubbornly refusing to change one's opinion or chosen course of action.

Obstreperous: Noisy and difficult to control.

Obstructive: Causing a blockage or obstruction.

Obtainable: Able to be obtained.

Obtained: Acquired or received.

Obtrusive: Noticeable or prominent in an unwelcome or intrusive way.

Obtuse: Annoyingly insensitive or slow to understand.

Obvious: Easily perceived or understood; clear.

Occasional: Occurring, appearing, or done infrequently and irregularly.

Occult: Related to magical or supernatural powers and activities.

Occupational: Related to one's job or profession.

Oceanic: Relating to the ocean.

Odd: Different from what is usual or expected; strange.

Oddball: A strange or eccentric person.

Oddish: Somewhat odd or strange.

Odious: Extremely unpleasant; repulsive.

Odorless: Having no odor.

Odorous: Having or giving off a smell.

Oenological: Relating to the study of wines.

Offbeat: Unconventional or unusual.

Offensive: Causing someone to feel deeply hurt, upset, or angry.

Offhand: Ungraciously or offensively nonchalant or cool in manner.

Offhanded: Casual or informal.

Official: Relating to an authority or public body and its duties, actions, and responsibilities.

Officious: Assertive of authority in an annoyingly domineering way.

Oily: Covered with or resembling oil.

Old-fashioned: In or according to styles or types no longer current.

Old: Having lived for a long time; no longer young.

Oleaginous: Rich in, covered with, or producing oil; oily.

Olympic: Relating to the ancient city of Olympia or the Olympic Games.

Ominous: Giving the impression that something bad or unpleasant is going to happen.

Omnipotent: Having unlimited power.

Omniscient: Knowing everything.

Omnivorous: Eating both animal and plant foods.

Oncoming: Approaching or coming closer.

One-eyed: Having only one eye.

One-legged: Having only one leg.

One-sided: Unfairly balanced in favor of one side.

One-time: Occurring, done, or used on one occasion.

One-way: Allowing movement in one direction only.

Onerous: Involving a great deal of effort, trouble, or difficulty.

Onetime: Occurring once.

Ongoing: Continuing without interruption.

Onshore: Located on or near the shore.

Onstage: On the stage in a theater.

Ontological: Relating to the branch of metaphysics dealing with the nature of being.

Opaque: Not able to be seen through; not transparent.

Open-ended: Having no defined limit or end.

Open: Allowing access, passage, or a view through an empty space.

Operable: Capable of being used; in working order.

Operatic: Relating to or characteristic of opera.

Operative: Functioning or having effect.

Opinionated: Holding stubbornly and often unreasonably to one's own opinions.

Opponent: Someone who competes or argues against someone else.

Opportune: Well-timed or suitable.

Opportunistic: Taking immediate advantage, often unethically, of any circumstance of possible benefit.

Opposable: Capable of being placed opposite to something.

Opposed: Eager to prevent or put an end to; disapproving of or disagreeing with.

Opposite: Completely different; of a contrary kind.

Oppositional: In opposition or resistance.

Oppressive: Unjustly inflicting hardship and constraint, especially on a minority or other subordinate group.

Optimal: Best or most favorable.

Optimistic: Hopeful and confident about the future.

Optimized: Made as effective as possible.

Optional: Available to be chosen but not obligatory.

Opulent: Ostentatiously rich and luxurious or lavish.

Oracular: Relating to an oracle.

Oral: Pertaining to the mouth.

Orange-flavored: Having the flavor of orange.

Orange: Of the color between red and yellow; like that of a ripe orange.

Orbital: Relating to an orbit or orbits.

Orbiting: Moving in orbit around something.

Orderly: Neatly and methodically arranged.

Organic: Relating to or derived from living matter.

Organically-grown: Grown without the use of synthetic chemicals.

Organizational: Related to the organization of something.

Orgasmic: Relating to orgasm.

Oriental: Relating to the countries of the East.

Original: Present or existing from the beginning; first or earliest.

Ornamental: Serving as a decoration.

Ornate: Made in an intricate shape or decorated with complex patterns.

Ornery: Bad-tempered and combative.

Orthodox: Conforming to what is generally or traditionally accepted as right or true.

Oscillating: Moving or swinging back and forth in a regular rhythm.

Ossified: Turned into bone or bony tissue.

Ostensible: Stated or appearing to be true, but not necessarily so.

Ostentatious: Characterized by vulgar or pret

Other: Denoting a person or thing that is different or distinct from one already mentioned or known.

Outback: Remote rural country.

Outbound: Traveling away from a particular place.

Outcast: A person who has been rejected by society or a social group.

Outdated: No longer current or in fashion.

Outer: Located on the outside.

Outfield: The area of a baseball field beyond the infield.

Outgoing: Friendly and socially confident.

Outlandish: Looking or sounding bizarre or unfamiliar.

Outlawed: Made illegal.

Outlying: Distant or remote.

Outmoded: No longer fashionable or useful.

Outrageous: Shockingly bad or excessive.

Outside: Situated or moving beyond the boundaries or confines of something.

Outspoken: Frank and unreserved in speech.

Outspread: Fully extended or stretched out.

Outstanding: Exceptionally good.

Outward: Directed toward the outside or away from a central point.

Oval: Having a rounded and slightly elongated outline or shape.

Overabundant: Excessively abundant.

Overactive: Excessively active.

Overaged: Too old.

Overaggressive: Excessively aggressive.

Overambitious: Excessively ambitious.

Overbearing: Domineering or bossy.

Overblown: Excessively inflated or exaggerated.

Overbooked: Accepted more reservations than can be accommodated.

Overburdened: Loaded with too much responsibility.

Overcast: Covered with clouds or dull.

Overcautious: Excessively cautious.

Overconfident: Excessively confident.

Overcrowded: Filled beyond capacity.

Overdone: Cooked too much.

Overdressed: Dressed too formally or elaborately.

Overdue: Not having arrived, happened, or been done by the expected time.

Overeager: Excessively eager.

Overemotional: Excessively emotional.

Overenthusiastic: Too enthusiastic.

Overextended: Stretched beyond reasonable limits.

Overfilled: Filled beyond capacity.

Overflowing: So full that it spills over.

Overgrown: Covered with excessive growth.

Overhanging: Hanging over something.

Overheated: Excessively hot.

Overjoyed: Extremely happy.

Overlapping: Extending over and covering part of something else.

Overloaded: Given too much to handle.

Overlooked: Not seen or noticed.

Overpaid: Paid more than necessary.

Overpopulated: Having too many people.

Overpowering: Extremely strong or intense.

Overpriced: Costing too much.

Overprotective: Excessively protective.

Overqualified: Having more qualifications than needed.

Overrated: Given more praise than deserved.

Overriding: More important than any other considerations.

Overrighteous: Excessively or hypocritically pious.

Overripe: Too ripe.

Overrun: Spread over or occupy (a place) in large numbers.

Oversensitive: Excessively sensitive.

Oversized: Larger than normal or expected.

Overstated: Exaggerated.

Overstuffed: Filled too full.

Overt: Done openly and plainly.

Overused: Used too often.

Overvalued: Valued too highly.

Overweight: Weighing more than is healthy.

Overwhelming: Very great in amount.

Overwrought: Agitated or anxious.

Oxidized: Combined with oxygen.

Oxyacetylene: Pertaining to a mixture of oxygen and acetylene.

Oxygenated: Enriched with oxygen.

Oxymoronic: Containing contradictory terms.