- ordination
- Old Nick
- overtire
- off the latch
- overwrite
- off-course
- on dry land
- off the subject
- on an equal footing
- ordered
- on every side of
- outstretch
- on numerous occasions
- old boy
- orbiting
- one or two
- obtrusion
- on the slate
- over-appreciative
- officers of the law
- off the top of one's head
- orient oneself
- on everyone's lips
- on the bias
- one-party
- on one' own
- on the attack
- on the right lines
- orison
- on the quiet
- one after the other
- occultation
- obscenities
- old-world
- on the strength of
- omitted
- one of a kind
- one's advancing years
- old saw
- opencast mine
- old-maidish
- old codger
- overdraw
- out of touch with reality
- of value
- outer edge
- on record
- otherworldly
- on a level with
- orbshaped
- on the wagon
- opening statement
- of unsound mind
- oppugnant
- ornithologist
- on the never-never
- odysseys
- offal
- oceanic
- out of shape
- only now
- of no value
- overtired
- on the same wave-length
- on the assumption that
- of the wall
- open to doubt
- of the order of
- one's cards
- occupied with
- out of harmony
- of yore
- one-eighty
- only to be expected
- outpace
- over-wrouht
- one's career
- of the utmost importance
- open one's mouth
- overburden
- on the map
- oral tradition
- on offer
- on the lookout
- overvalue
- occupier
- old lady
- overplay
- outback
- outstanding payment
- oddment
- oriel
- outst-anding
- out of line
- objectives
- once and for all
- overnighter
- obsolescence
- ovid
- of the old school