- one who uses high_sounding sentences to create effect
- one who knows persian
- one who makes sarcastic remarks
- of the colour
- open(ed)
- only alone
- order eubacteriales
- order eubryales
- one hundred fifty
- open fire
- ovoid skull
- oviviviparous
- oral contraceptive pill
- old lady
- ogler
- old world
- old wives' tale
- old school
- onomatopoeical
- optical disc
- optical disk
- osmitrol
- osmo receptor
- oreide
- oroide
- outshout
- oily substance
- one who shows off a lot
- one who plays on
- one of the trinity of mythological hindu deities
- oust
- office of inspector general
- oil aspiration pneumonia
- oil company
- operant conditioning
- operate
- outlast
- out in
- Ononis repens
- Ononis spinosa
- old_maid's bonnet
- office furniture
- outdoorsman
- orthopaedist
- oncologist
- orthopedist
- ophthalmologist
- orthoptist
- orgy
- orgiastic