- oil immersed
- otus scops
- Otus sunia
- one of the ceremonies held at the bride's door during the marriage
- ottos pelvis
- orestes
- or to be under one's thumb
- or to go into a sleep as if never to awake
- opistho_
- oolong
- olecranon
- or (figuratively) to take to an ascetic's attire
- oregon crab apple
- Old Irish
- organ of uropoetica
- ocotea pretiosa
- otto the great
- otto i
- omphalotomy
- ozonise
- ozonize
- opisthognathism
- orthopnoea
- oligonucleotide
- orange fleabane
- orange daisy
- orrisroot
- orris
- oriental learning
- on daily wages
- one who harmonizes
- old faithful
- old flame
- oto_basion inferius
- organophosphate
- oto_basion superius
- one who does a good turn in return
- one who laments
- oleomargarine
- on the side
- one_step
- object library
- or aiming at
- Old North French
- Old French
- object oriented language
- on earth
- oxyphenylethylamine
- of unknown lineage
- one of the three main canals of the body (the other two being