- ophthalmic
- ophthalmologist
- opine
- opinionative
- off duty
- opium-den
- on account of
- on cloud nine
- oracle
- orange tree
- orchestra man
- orchestrate
- ordeal
- oxygen mask
- ostentation
- osteomalacia
- ostracize
- ostrich policy
- otalgia
- overweight
- overturn
- otherwise
- oversea, overseas
- overreact
- out of sorts
- out of spirits
- out of temper
- overpowering
- out of the straight
- overindulge
- overheads
- outcry
- outdoor
- outer
- outface
- outfitter
- outflow
- outgrowth
- outlay
- over live
- ovational
- ovaritis
- ovarian
- outpoint
- outrageous
- outside
- outskirts
- outweigh
- outward
- out of one's mind
- one who ignores household duties as laid down by the scriptyres
- one who gives joy
- one who erects
- of course
- one who collects customs-tax
- one who acts
- on the rove
- on the nail
- on no account
- on cost
- on a par witih
- omnipresence
- ominous
- out of nowhere
- ology
- oil nuts
- oh save!
- officious
- officinal
- off and on
- oddity
- odd jobs
- out of doors
- out cold
- oculist
- octuple
- oceanus
- ocean
- occurence
- oscillatory
- occident
- obvious
- os
- obtrusive
- observing
- oryx
- observation
- obscurity
- obey
- orthographic
- obeisance
- oarsman
- oafish
- option
- overawed
- on sight
- oestrogen
- orchid
- optical centre
- out of job