| Acronym | Definitions |
|---|---|
| ORSR | 2 |
| ORSTOM | 4 |
| ORT | 8 |
| ORTA | 2 |
| ORTHO | 5 |
| ORTP | 2 |
| ORTS | 2 |
| ORU | 4 |
| ORV | 3 |
| ORWH | 1 |
| OS | 33 |
| OS&D | 3 |
| OS/2 | 1 |
| OS/VS | 1 |
| OSA | 19 |
| OSAC | 2 |
| OSAF | 1 |
| OSAP | 2 |
| OSB | 6 |
| OSC | 19 |
| OSCAR | 10 |
| OSCE | 4 |
| OSCP | 2 |
| OSCR | 3 |
| OSD | 10 |
| OSDA | 2 |
| OSDBU | 1 |
| OSDF | 2 |
| OSDH | 2 |
| OSDIT | 1 |
(631 — 660 of 831)