| Abbreviation | Definition |
|---|---|
| OFM | Order of Fat Men |
| OFT | On-line Family Tree |
| OFV | Ontario Federation of VANNERS |
| OG | Online Gaming |
| OG | Original |
| OGD | Orchid Guide Digest |
| OGR | O Gauge Railroading |
| OHMS | Oregon Historical Modelers Society |
| OhMyYo | Inside Joke from our Grade 5/6 class |
| OJC | Ocala Jeep Club |
| OJG | Official J-Rock Glompers |
| OMP | OneModelPlace.Com |
| ONT | Orchid Society of Northern Transvaal |
| OOAK | One Of A Kind |
| OOB | Out Of Box |
| OOM | Out Of Mana |
| OOT | Ocarina Of Time |
| OOTF | Order of the Force |
| OPE | Outdoor Power Equipment |
| OPMF | Over Powered Mother F***er |