| OROS | oral osmotic |
|---|---|
| ORT | object relations technique; operating room technician; oral rehydration therapy |
| OS | left eye [Lat. oculus sinister]; occipitosacral; occupational safety; office surgery; Omenn syndrome... |
| OSCC | oral squamous cell carcinoma |
| OTD | oculotrichodysplasia; oral temperature device; organ tolerance dose |