| OI | obturator internus; occasional insomnia; opportunistic infection; opsonic index; orgasmic impairment... |
|---|---|
| OID | optimal immunomodulating dose; Organism Identification Number; oxygen insufflation device |
| OPP | osmotic pressure of plasma; oxygen partial pressure |
| ORM | orosomucoid; other regulated material; oxygen ratio monitor |
| ORMC | oxygen ratio monitor controller |