| Abbreviation | Definition |
|---|---|
| OFCAF | On-Farm Climate Action Fund |
| OFEP | Oregon Forestry Education Program |
| OG | Operational Guideline(s) |
| OGM | Oil Gas Minerals |
| OGSG | Ogun State Sanitation Group |
| OHASA | Occupational Hygiene Association of South Africa |
| OIEE | Oxford Institute for Environmental Education |
| OIW | Oil-in-Water |
| OLEM | Office of Local Environmental Management |
| OMC | OM Chanting |
| OMND | Oliver-Mercer-North Dunn |
| OMRDD | Office of Mental Retardation and Developmental Disabilities |
| OMRR | Organic Matter Recycling Regulation |
| ONEB | Office of National Environmental Board |
| ONES | Outstanding New Environmental Scientist |
| OPDES | Oklahoma Pollutant Discharge Elimination System |
| OPEA | Office of Planning Environmental Analysis |
| OPEP | Oil Pollution Emergency Plans |
| OPET | Oyster Pond Environmental Trust |
| OPITO | Offshore Petroleum Industry Training Organization |