- orbiting
- Oxford blue
- operating costs
- old fashioned
- owing a debt of gratitude
- oatmeal
- outreach
- old warhorse
- obtrusion
- of little importance
- of one voice
- owing to the fact that
- on the jungle telegraph
- outpost
- one hundred percent
- overtire
- on vacation
- on bended knee
- okey-dokey
- Old Nick
- odysseys
- on everyone's lips
- of the order of
- only to be expected
- open to doubt
- opencast mine
- outer edge
- overnighter
- outback
- ovid
- on the right lines
- on a level with
- overburden
- on record
- of unsound mind
- orison
- on the lookout
- oral tradition
- of value
- offal
- occupied with
- old codger
- over-wrouht
- on the assumption that
- overdraw
- omitted
- off the top of one's head
- once and for all
- oceanic
- old-world
- on the bias
- one-party
- out of touch with reality
- orient oneself
- oriel
- on the never-never
- on the same wave-length
- of yore
- out of line
- of the old school
- on the quiet
- on the attack
- one of a kind
- objectives
- outstanding payment
- of the utmost importance
- overplay
- one after the other
- out of harmony
- one-eighty
- occupier
- of the wall
- on the map
- open one's mouth
- old saw
- opening statement
- obsolescence
- on the strength of
- only now
- orbshaped
- on one' own
- old lady
- overvalue
- old-maidish
- on the wagon
- otherworldly
- obscenities
- ornithologist
- outpace
- of no value
- on offer
- oppugnant
- overtired
- oddment
- out of shape
- one's advancing years
- outst-anding
- one's cards
- one's career
- occultation