- ovarian pregnancy
- omelette
- omelet
- over_ whelmed by emotion
- operative surgery
- of hundred years (of age)
- opioid antagonist
- of own making
- own label
- odontoblastic process
- ostracize
- on the head
- overtransfusion
- one who removes
- offering (to relatives)
- outspread
- one man
- options
- optical iridectomy
- otologist
- on edge
- of the essence
- on the breadline
- one's wife
- outpatient
- onychomycosis
- occlusive bandage
- order to appear before
- olfactory
- overrun error
- open case
- osteosclerotic anaemia
- of equal weight
- of youthfulness
- object time
- object deck
- object pack
- one another
- operate mode
- ovarian abscess
- ovarian aplasia
- ovarian plexus
- ovarian cycle
- opisthocranion
- outdatedness
- olecranon height index
- organ transplant
- on tail
- octave of frequency
- or to be under one's thumb