| OR | a logical binary relation that is true if any argument is true, and false otherwise; [o]estrogen rec... |
|---|---|
| ORALABX | oral antibiotics |
| ORD | optical rotatory dispersion; oral radiation death |
| OROS | oral osmotic |
| OS | left eye [Lat. oculus sinister]; occipitosacral; occupational safety; office surgery; Omenn syndrome... |