| MSSA | MA Student Services Administration 
| Others |
| MSSA | Maine School Superintendents Association
| Others |
| MSSA | Malaysian Singaporean Students Association
| Others |
| MSSA | Mansoura Students Scientific Association
| Others |
| MSSA | Maryland Saltwater Sportfishermens Association
| Others |
| MSSA | Maryland State Soccer Association
| Others |
| MSSA | Maryland State Sportsmen's Association
| Others |
| MSSA | Master of Science in Social Administration
| Others |
| MSSA | Master Service and Supply Agreement
| Others |
| MSSA | Master Supplier Services Agreement
| Others |
| MSSA | Medical Service Study Areas
| Others |
| MSSA | Medical Student Society Association
| Others |
| MSSA | Medical Students Society and Association
| Others |
| MSSA | Memphis Sport Shooting Association
| Others |
| MSSA | Mess Management Specialist Seaman Apprentice
| Others |
| MSSA | Mess Specialist Seaman Apprentice
| Others |
| MSSA | methicillin sensitive S aureus
| Others |
| MSSA | Methicillin sensitive staph and
| Others |
| MSSA | Methicillin Sensitive Staph Aureus
| Others |
| MSSA | Methicillin Sensitive Staphylococcus Aureus
| Others |
| MSSA | Methicillin Susceptible S Aureus
| Others |
| MSSA | Methicillin Susceptible Staphylococcus Aureus
| Others |
| MSSA | Methicillin Susceptible Strains Abbreviation
| Others |
| MSSA | Methicillin-Ausceptible Staphylococcus Aureus
| Others |
| MSSA | Methicillin-Sensitive Staphylococcus Aureus
| Others |
| MSSA | Meticillin sensitive Staphylococcus aureus
| Others |
| MSSA | Microscopy Society of Southern Africa
| Others |
| MSSA | Microsoft Software and Systems Academy
| Others |
| MSSA | Microsoft Software Systems Academy
| Others |
| MSSA | Microsoft South Africa
| Others |
| MSSA | Mid South Sign Association
| Others |
| MSSA | Mid South Sociological Association
| Others |
| MSSA | Mid-South Sociological Association
| Others |
| MSSA | Middlesex School Summer Arts
| Others |
| MSSA | Mikuni Shimokawa Seishun Anime
| Others |
| MSSA | Military Selective Service Act
| Others |
| MSSA | Military Style Semi Automatic
| Others |
| MSSA | Military-Style Semi-Automatic
| Others |
| MSSA | Mind Sports South Africa
| Others |
| MSSA | Minnesota Social Service Association
| Others |
| MSSA | Minnesota State Student Association
| Others |
| MSSA | Missouri Sport Shooting Association
| Others |
| MSSA | Montana Shooting Sports Association
| Others |
| MSSA | Monteagle Sunday School Assembly
| Others |
| MSSA | Montessori School of San Antonio
| Others |
| MSSA | Montreal Student Space Associations
| Others |
| MSSA | More Super Soaker Action
| Others |
| MSSA | Mormon Social Science Association
| Others |
| MSSA | Mount Sinai Sailing Association
| Others |
| MSSA | Mountain States Stockdog Association
| Others |
| MSSA | Mssamanoa School Student Association
| Others |
| MSSA | Multi Sensor Surveillance Aircraft
| Others |
| MSSA | Multi Service Storage Architecture
| Others |
| MSSA | Multiclass Spatial Stagewise Aggregation
| Others |
| MSSA | Multiple Sclerosis Services Agency
| Others |