| Abbreviation | Definition |
|---|---|
| OHCC | Outer Harbour Centreboard Club |
| OHSC | Oak Hollow Sailing Club |
| OHSC | Oregon Homeschool Science Club |
| OHSC | Ouran High School Club |
| OHTC | Oakland Hills Tennis Club |
| OJC | Ontario Jockey Club |
| OJSC | Onslow Junior Soccer Club |
| OJSC | Orange Jr Soccer Club |
| OJSC | Orange Junior Soccer Club |
| OLC | Omaha Lacrosse Club |
| OLCC | Old Leightonians Cricket Club |
| OLRC | Oquirrh Lake Radio Club (South Jordan, Utah) |
| OLTC | Oegstgeester Lawn Tennis Club |
| OLYC | Okauchee Lake Yacht Club (Oconomowoc, WI) |
| OMAC | Old Montauk Athletic Club |
| OMAC | Onondaga Model Aircraft Club |
| OMBAC | Old Mission Beach Athletic Club |
| OMBC | Old Monmothians Boat Club |
| OMBC | Overland Mountain Bike Club |
| OMC | Olitaire Millionaires Club |