- order of events
- ornithology covert
- obduracy
- Our Lord
- oral communication
- on a par with
- overtax oneself
- orchard
- of no matter
- occurring
- open-handedness
- oppressiveness
- over-fastidious
- on any account
- OAP
- on tick
- of immeasurable value
- overwhelm-ing
- overpriced
- outrush
- OTT
- on deck
- over-refined
- out of style
- out of action
- organizational
- object d'art
- Ozalid
- overfull
- off drugs
- over the odds
- observed
- over-elaborateness
- open to change
- outcrop
- obstacles
- old boy
- other woman
- on your way
- outrageousness
- one after another
- overzealous
- on end
- onrush
- on top of that
- owing to the fact that
- on vacation
- owing a debt of gratitude
- oatmeal
- outpost
- other side of the coin
- Old Nick
- overtire
- okey-dokey
- obtrusion
- orbiting
- outreach
- on bended knee
- old warhorse
- on the jungle telegraph
- one hundred percent
- of one voice
- Oxford blue
- of little importance
- old fashioned
- on the right track
- operating costs
- on every side of
- of age
- ordered
- on dry land
- one-sidedness
- overlord
- one's marching orders
- opponents
- on an equal footing
- one or two
- over-appreciative
- of no moment
- outflux
- on the verge of tears
- owing someone a debt of gratitude
- of immeasurable worth
- off the latch
- oiled
- one's lot in life
- others
- overwrite
- of a kind
- ocean-going
- on numerous occasions
- of the cuff
- officers of the law
- outturn
- over-sensational
- obiter dictum
- open-work
- overspend
- on the block
- opposers