| Abbreviation | Definition |
|---|---|
| OJ | Orenthal James |
| OJ | Orenthal James Simpson |
| OJ | Oscar Johnson |
| OJS | Orenthal James Simpson |
| OK | Orrins Kendall |
| Olly | Oliver Stanley (musician) |
| OMH | Old Mother Hubbard |
| ONJ | Olivia Newton- John |
| OOTP | Order of the Phoenix |
| OS | O Sullivan |
| OSC | Orson Scott Card (Sci-fi author) |
| OW | Oscar Wilde |
| OWH | Old Weird Herald |
| P | Pavarotti |
| P | Peabody |
| PA | Prince Albert |
| PAKC | Pamela Kelso Craig, artist |
| PB | Padington Bear |
| PB | Phillip Barrow |
| PB | Poo Bear |