| | oot | | Object-Oriented Technology |
| | oot | | out |
| | oot | | Out Of Touch |
| | oot | | out of town |
| | OOTC | | Obligatory On Topic Comment |
| | OOTD | | one of these days |
| | OOTO | | out of the ofice |
| | OOTQ | | Out Of The Question |
| | ootw | | out of this world |
| | opac | | on-line payment and collection |
| | opac | | online public access catalogues |
| | OPD | | Obnoxious Personality Disorder |
| | OPEC | | Organization of Petroleum Exporting Countries |
| | OPL | | obvious panty line |
| | OPM | | Other People's Money |
| | OPM | | Other Peoples Money |
| | opp | | Other People's Problems |
| | OPUSH | | OBEX Object Push |
| | ORV | | Off Road Vehicle |
| | os | | operating system |
| | OSD | | Object Based Storage Device |
| | OSD | | Object Storage Device |
| | OSD | | On-Screen Display |
| | OSDNMAS | | One salad does not make a slimmer |
| | OSDNMAS | | One Swallow Does Not Make A Summer |
| | OSEK | | Open systems and the Corresponding Interfaces for Automotive Electronics |
| | OSH | | Occupational Safety and Health Administration |
| | osha | | occupational safety and health administration |
| | OSIF | | Oh sh*t I Forgot! |
| | OSIM | | Oh sh*t Its Monday |
|