| Acronym | Definition |
|---|
| POSA | President of South Africa |
| POSA | Public Order and Security Act |
| POSA | Partners of Sex Addicts |
| POSA | Point of Sale Activation |
| POSA | Pattern Oriented Software Architecture |
| POSA | Person of Ordinary Skill in the Art (patent law) |
| POSA | Politics of Open Source Adoption |
| POSA | Proceed-on-Sight Authority (UK) |
| POSA | Passive Optical Sample Assembly |
| POSA | Pembroke Old Scholars' Association (Australia) |
| POSA | Pinner Old Students Association (UK; alumni association) |
| POSA | Parks and Open Space Advocates (Seattle, WA) |
| POSA | Preliminary Operation Safety Analysis |
| POSA | Payments Outstanding Suspense Account |
| POSA | Pacific Ocean Shipping Agency (Egypt) |
| POSA | Pomona College Student Art Gallery (Claremont, California) |
| POSA | Pride of Sheffield Ave. (New York fire station) |