| Acronym | Definition |
|---|
| MSSA | Mind Sports South Africa |
| MSSA | Microsoft Software & Systems Academy |
| MSSA | Methicillin-Sensitive Staphylococcus Aureus |
| MSSA | Medical Service Study Area (California) |
| MSSA | Military Selective Service Act |
| MSSA | Military Style Semi-Automatic Firearm (classification, New Zealand) |
| MSSA | Musis Sacrum Schouwburg Arnhem (Dutch theater) |
| MSSA | Microscopy Society of Southern Africa |
| MSSA | Maryland Saltwater Sportfishermen's Association |
| MSSA | Mid-South Sociological Association |
| MSSA | Microscopy Society of America |
| MSSA | Mississauga Synchronized Swimming Association (Canada) |
| MSSA | Minnesota Social Service Association |
| MSSA | Multi-Channel Singular Spectral Analysis |
| MSSA | Missouri Sport Shooting Association (Columbia, MO) |
| MSSA | Mid South Sign Association |
| MSSA | Master of Science in Social Administration (Case Western Reserve University, Cleveland, Ohio) |
| MSSA | Memphis Sport Shooting Association |
| MSSA | Master Service and Supply Agreement (contracts) |
| MSSA | Modified Selective Severity Assessment (substance abuse) |
| MSSA | Master Safeguards and Security Agreement |
| MSSA | Monteagle Sunday School Assembly (Monteagle, TN) |
| MSSA | Multi Sensor Surveillance Aircraft (Westinghouse, Baltimore) |
| MSSA | Mansoura Students' Scientific Association (Mansoura, Egypt) |
| MSSA | Mobile Self-Storage Association |
| MSSA | Middle School Soccer Association |
| MSSA | Microsoft Security Support Alliance |
| MSSA | Mission Supply Support Activity |
| MSSA | Malaysian Steel Structure Association |
| MSSA | Middlesex School of Summer Arts (Concord, MA) |
| MSSA | Mission Supply Support Account (US Army) |
| MSSA | Montessori School of San Antonio (Texas) |
| MSSA | Multiscale Statistical Signal Analysis |
| MSSA | Microsoft South Africa |
| MSSA | Managed Services Service Assurance |
| MSSA | Manchester Student Society of Architects (UK) |