| OC | obstetrical conjugate; occlusocervical; office call; on call; only child; optic chiasma; oral contra... |
|---|---|
| OPO | Organ Procurement Organization |
| OS | left eye [Lat. oculus sinister]; occipitosacral; occupational safety; office surgery; Omenn syndrome... |
| OSF | organ system failure; osteoclast-stimulating factor; outer spiral fiber; overgrowth stimulating fact... |
| OTD | oculotrichodysplasia; oral temperature device; organ tolerance dose |