- on the turn
- on the understanding
- on the score of absurdity
- oncoming
- onerous
- open one's eyes
- one hundred thousand
- one man rule
- one who has taken an additional wife
- one who lives by his writing
- only-begotten
- overwhelm
- onus probandi
- operate
- operatic
- operating system
- operoseness
- one more
- occur to one
- off settle
- out attire
- out consume
- on one's own
- on stockpile
- on enchant
- on disparage
- on the back praise
- one's stride cope with easily
- one's ground
- one thinks fit
- oldage pensioner
- order off
- out of the public eye
- old horse
- of around
- outdoor meal
- of the same mind
- outdoors
- oldness
- of the Middle Ages
- on exploit
- outhouse
- over-powered
- on hire purchase
- out of one's element
- off the mark
- on one's father's side
- out of breath
- out of devastate
- obey the rules
- out of someone drain
- of no importance
- on the slant
- opinion poll
- open framework
- out of public view
- oral examination
- original inhabitant
- one by one
- on draught
- out of favour
- outrider
- off guard
- over ignore
- opposing side
- open space
- of little consequence
- one time
- on attach great importance to
- out pay
- out of reach
- official procedure
- orgasm
- officials
- optimistically
- office worker
- ordering back
- of greatest import-ance
- out show
- on-the-spot
- orchestra musical group
- off escape
- official communica-tion
- out of one's hands
- on regulate
- obedience to
- on all sides
- oxidation
- on take pride in
- objector
- off get over
- outsource
- over-particular
- or
- on the same level as
- out check
- one's thumbs be idle
- out disregard
- off-white
- old-age pension