| Abbreviation | Definition |
|---|---|
| OPC | Original Post Count |
| OPIN | Only Person I Need |
| OPKE | Open Person Killing Entity |
| OPLB | One Piece Lovers Batam |
| OPPM | One Post Per Minute |
| ORIMIN | Origami Mindaugas |
| ORLY | Oh Really?! |
| ORN | Obligatory Running Note |
| ORT | Organically Reproduced Trash |
| OS | Oneself |
| OSAMI | Oxymoron, Such As Military Intelligence |
| OSC | Obvious Spotters Crew |
| OSC | Our Secret Club |
| OSC | Our Super Clan |
| OSG | One Sweet Guy |
| OSLT | Or Something Like That |
| OSO | Other Significant Others |
| OSR | Oh S*** Run |
| OSS | Oh So Social |
| OSS | On Some S*** |