- over worn
- out in the cold
- over sleepy
- outshine
- outer rind
- out of number
- overcompensate
- overlordship
- order from the top
- output
- outfit
- over praising
- open-hearted
- over-age
- ornithophily
- onanimpulse
- orthogonal
- oblative case
- out on a limb
- on the line
- out of luck
- outnumbered
- off the record
- on the point of
- on the move
- overdo
- obligatory
- obsessive
- obsolescent
- obtuse
- occlude
- over and over
- ointment
- once
- ooze
- oppression
- orator
- organ
- ostensible
- out of the way
- outlive
- out of work
- opulent
- overblown
- overflowing
- overhang
- overpower
- overrule
- overture
- overused
- overwhelming
- opposite
- off pat
- old person
- outmanoeuvre
- of late
- out of print
- offspring
- objection
- once in a blue moon
- ordinal
- opalize
- overstatement
- oversexed
- overseer
- override
- overhead
- on the sidelines
- over fond
- ox
- ownership
- on the trot
- ovation
- on the wane
- oceanid
- orange plant
- opener
- out of phase
- overdress
- opposite view
- oversimplification
- of one's own
- oviferous
- out-take
- oxfam
- organogram
- off-time
- oxonian
- overbid
- overween
- official despatches
- osteoporosis
- oceania
- outside work
- on the right side of forty
- open newel
- overground
- ovenware
- orbicularity
- opposite course