- oink
- ointment
- ointment for burns
- okapi
- okay
okra
- OLC
- old
- old age
- old before one's time
- old beyond one's years
- Old boy!
- old degree
- old enough to be s.b.'s father/ mother
- Old Face
- old folks' home
- old hat
- old people's home
- Old Testament
- old, unhappy, far-off things
- old-established
- old-fashioned
- old-time
- old-timer
- older
- oldest
- oldish
- oldster
- oleander
- oleograph
- olfactory

