| Abbreviation | Definition |
|---|---|
| OCA | Ontario Cattlemen's Association |
| OCAA | Ontario Colleges Athletic Association |
| OCAA | Ontario Conference of Casualty Actuaries |
| OCAA | Oregon City Attorneys Association |
| OCAW | Oil, Chemical, and Atomic Workers |
| OCCA | Oil and Colour Chemists' Association (UK based) |
| OCDP | Ohio Chemical Dependency Professionals |
| OCDS | Orange County Dental Society |
| OCIA | Ociationorganic Crop Improvement Association |
| OCIA | Oklahoma Crop Improvement Association |
| OCIA | Onal Crop Improvement Association |
| OCIA | Organic Crop Improvement Association |
| OCIA | Ormationorganic Crop Improvement Association |
| OCIMF | Oil Companies International Marine Forum |
| OCM | Organization Change Management |
| OCMA | Ohio Community Mediation Association |
| OCMA | Ohio Concrete Masonry Association |
| OCMA | Ontario Colleges Mathematics Association |
| OCNA | Ontario Community Newspaper Association |
| OCPA | Ontario Concrete Pipe Association |