| OH | hydroxycorticosteroid; obstructive hypopnea; occipital horn; occupational health; occupational histo... |
|---|---|
| OHS | obesity hypoventilation syndrome; occipital Horn syndrome; occupational health service; ocular histo... |
| OMVC | open mitral valve commissurotomy |
| OPA | open procurement agency |
| OR | a logical binary relation that is true if any argument is true, and false otherwise; [o]estrogen rec... |