| WPk | Ward's pack; wet pack |
|---|---|
| OR | a logical binary relation that is true if any argument is true, and false otherwise; [o]estrogen rec... |
| ORS | olfactory reference syndrome; oral rehydration solution; oral surgery, oral surgeon; Orthopaedic Res... |
| OS | left eye [Lat. oculus sinister]; occipitosacral; occupational safety; office surgery; Omenn syndrome... |
| misc | miscarriage; miscellaneous |