- odoroside h
- odynphagia
- odour value
- o.e.d.
- os frontale
- occupation neurosis
- occular sympathetic paralysis
- order oedogoniales
- oesophageal regurgitation
- oesophagoplasty
- oesophagojejunal anastomosis
- oesophagoscopy
- oestrin
- oestrual cycle
- oesophagogastric anastomosis
- oesophagus kymography
- oestrogen dependent
- oesophagotomy
- outbound
- offshore
- ommatidium
- orange zest
- oxygenator
- oysters Rockefeller
- opsoclonia
- ops
- oxford vaporizer
- oxidative fusion
- oxophenarsine
- oxido_reductases
- oxiranes
- oxoid
- ousel
- orange group
- ovarian amenorrhoea
- over exposure
- otc
- overbite
- overcall
- overbreathing
- overflow position
- o.d.
- overdubbing
- open_end credit
- oversewn
- overlay tree
- overlapping generation
- overlap test
- overprinting
- overton theory