| 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 |
| ORS | olfactory reference syndrome; oral rehydration solution; oral surgery, oral surgeon; Orthopaedic Res... |