page 16 for the letter O
- oilseed rape
- oilskin
- oilstock
- oilstone
- oilstove
- oiltight
- oily
- ointment
- Oireachtas
- oiticica
- OJ
- ojo
- oka
- okapi
- okay
- oke
- okey-doke
- okie
- Okinawa
- Okla.
- Oklahoma
- Oklahoma City
- okra
- old
- old age
- old-age allowance
- old-age pension
- old-age pensioner
- Old Bailey
- Old Bill
- old boy
- old-boy network
- Old Bulgarian
- Old Catholic
- Old Church Slavic
- old-clothesman
- old country
- Old Dominion
- Old English
- old-established
- old-fashioned
- old field
- old-field birch
- old-field pine
- old flame
- old-fogyish
- old girl
- Old Glory
- old gold
- Old Guard
- old hand
- Old Hickory
- Old High German
- Old Icelandic
- Old Ionic
- Old Irish
- old lady
- Old Lady of Threadneedle Street
- Old Latin
- Old Light
- old-line
- Old Line State