- on the fritz
- outer limit
- on the way out
- oddball
- overpopulated
- of no fixed address
- overfamili-arity
- on the eve of
- on the mend
- on the dot of something
- outcold
- on the go
- oldsters
- oppo. china
- outspokenness
- one's better half
- oldie
- on one's toe
- over the fence
- on the streets
- off Broadway
- out of true
- opium
- out of step with
- of distinction
- once-over
- offcut
- outrival
- one-horse
- of the highest quality superlative
- out-standing
- osteopathy
- otiose
- object of the exercise
- over-effusive
- outer reaches
- oddness
- overlooking
- on this account
- on one's beam-ends
- outperform
- other half
- oomph
- on one's lonesome
- oppo
- orthoepy
- one's dole
- on the understanding that
- one' cards
- out of hand
- of little account
- on one's Jack Jones
- on the bread-line
- oxbow
- of no account
- on that account
- offsider
- of moment
- opinions
- overstep
- overhasty
- outspokenly
- opaline
- omitting
- on the money. exclamation precisely
- on the ark
- on the fence
- overseeing
- out of control
- oil someone's palm
- osculate
- okay
- on the subject of
- on hold
- one in a million
- omnium gatherum
- on one's Pat Malone
- over the hill
- orotund. bombastic
- out of one's depth
- overpitch
- openhandedness
- one-off
- overlong
- on cloud seven
- outstandingly
- off center
- ombudsman
- over-adventurous
- on the rampage
- on the mark
- oldster
- on the breadline
- old womanish
- oik
- one-liners
- overexcited
- on the top of the world
- on us
- out of whack