One Word Substitutions Starting with O

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Oa – Oc

Oasis – Fertile spot in a desert

Obdurate – Stubborn, hard-hearted

Obedient – Willing to obey

Obituary – Notice of death in a newspaper

Objective – Goal, aim

Obliterate – To destroy completely

Oblivion – State of being forgotten

Obnoxious – Very unpleasant

Obscene – Offensive, indecent

Obsequious – Excessively submissive

Observatory – Place for observing stars/planets

Obsolete – Out of use

Obstetrician – Doctor specializing in childbirth

Obstinate – Stubborn

Obstruct – To block

Obtrude – To force upon

Obtuse – Dull-witted, slow

Obvious – Easily understood

Occasion – Particular event

Occult – Secret, mysterious

One Word Substitutions Starting with O

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Oc – Of

Occupation – One’s profession

Occurence – An incident

Octagon – Figure with eight sides

Octogenarian – Person between 80–89 years of age

Octopus – Eight-armed sea creature

Odyssey – Long adventurous journey

Offence – Violation of law

Offender – Wrongdoer

Office-bearer – Person holding an office/post

Officialdom – Body of officials

Officiate – To perform official duties

Oligarchy – Government by a few persons

Oligopoly – Market controlled by a few sellers

Omen – Sign of good/bad event in future

Omnipotent – All-powerful

Omnipresent – Present everywhere

Omniscient – All-knowing

Oncology – Study of cancer

Onomatopoeia – Words that imitate sounds

Onset – Beginning of something

One Word Substitutions Starting with O

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Op – Or

Opera – Dramatic performance set to music

Operetta – Short opera

Operator – One who controls a machine/system

Ophthalmologist – Eye specialist

Optimist – One who looks at bright side

Optometrist – Person who tests eyesight

Oration – Formal speech

Orator – Skilled public speaker

Orchestra – Group of musicians playing together

Ordain – Appoint as priest/minister

Ordeal – Severe trial/test

Ordinal – Number showing order (first, second, third)

Ordinary – Common, usual

Organism – Living being

Organization – A structured group

Ornament – Decorative item

Orphan – Child without parents

Orthodox – Following traditional beliefs

Orthography – Correct spelling

Orthopedics – Branch dealing with bones/joints

One Word Substitutions Starting with O

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Os – Ow

Oscillation – Back-and-forth movement

Ostensible – Appearing to be true but not necessarily so

Ostentation – Showy display of wealth/knowledge

Ostracism – Exclusion from society/group

Ostrich – Large flightless bird

Otology – Study of the ear and its diseases

Outcast – One rejected by society

Outlaw – Criminal hiding from law

Outspoken – Frank, candid

Outskirts – Outer parts of a city

Outstretch – Extend fully

Overestimate – To value too highly

Overhaul – Thorough examination and repair

Overjoyed – Extremely happy

Overpower – To defeat by force

Overrate – To give too much importance

Oversee – To supervise

Overthrow – To remove from power

Overture – Opening part of an opera/musical work

Overwhelm – To overpower emotionally/physically

One Word Substitutions Starting with O

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Advanced & Rare Vocabulary

Oblation – Offering to a deity

Obduracy – State of stubbornness

Obliquity – Deviation from morality

Obloquy – Public criticism or disgrace

Obsequy – Funeral rite

Ochlocracy – Mob rule

Occlude – Block, close up

Oenology – Study of wines

Olfactory – Related to the sense of smell

Oneirology – Study of dreams

Ontology – Study of existence/being

Opulence – Great wealth, luxury

Oracular – Prophetic, mysterious

Ornithology – Study of birds

Orthography – Study of correct spelling/writing

Ossuary – Container/place for bones of the dead

Ostler – Man employed to look after horses

Oxymoron – Figure of speech with contradictory terms

Oyster – Sea animal producing pearls

Ozonometer – Instrument to measure ozone

One Word Substitutions Starting with O

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One Word Substitutions Starting with N