- off-course
- open for discussion
- overspend
- obliviousness
- overarching
- overcurious
- outmost
- observation of
- or rather
- on numerous occasions
- of assistance
- outturn
- oviform
- overwrite
- open-work
- Ozalid
- on the block
- ocean-going
- obligated to
- over-sensational
- opening statement
- of the wall
- on the bias
- out of harmony
- on the map
- oddment
- only now
- over-wrouht
- overplay
- oppugnant
- objectives
- one's career
- one of a kind
- on the quiet
- out of line
- once and for all
- on the strength of
- of no value
- one's advancing years
- out of touch with reality
- on offer
- orbshaped
- overdraw
- on one' own
- obsolescence
- old-maidish
- ornithologist
- out of shape
- old codger
- oceanic
- omitted
- obscenities
- old saw
- on the lookout
- outstanding payment
- otherworldly
- outer edge
- outst-anding
- of the order of
- overnighter
- ovid
- on record
- one's cards
- overtired
- on the wagon
- on a level with
- one after the other
- outpace
- of the old school
- on the attack
- overburden
- outback
- of value
- overvalue
- old lady
- of the utmost importance
- occupier
- on the same wave-length
- on the never-never
- of yore
- orient oneself
- off the top of one's head
- old-world
- on everyone's lips
- of unsound mind
- occultation
- on the assumption that
- odysseys
- offal
- opencast mine
- open to doubt
- one-party
- only to be expected
- oral tradition
- on the right lines
- open one's mouth
- occupied with
- orison
- one-eighty
- oriel