| MSSO | Maharashtra Seva Samiti Organization 
| Others |
| MSSO | Mail Storage and Svc Operations
| Others |
| MSSO | Main Street South Orange
| Others |
| MSSO | Maintenance And Support Service Organisation
| Others |
| MSSO | Maintenance And Support Services Organization
| Others |
| MSSO | Maintenance Support Services Organisation
| Others |
| MSSO | Managed Single Sign On
| Others |
| MSSO | Management System Support Office
| Others |
| MSSO | Marine Survey And Systems Operation
| Others |
| MSSO | Marine Survey And Systems Operations
| Others |
| MSSO | Mean Squared Soft Output
| Others |
| MSSO | MedDRA Maintenance and Support Services Organization
| Medical, Organization |
| MSSO | Media Streaming Server System Overview
| Others |
| MSSO | Medical Scientist Student Organization
| Others |
| MSSO | Medical Students And Sites Officer
| Others |
| MSSO | Meteoor Super Spoed Opleiding
| Others |
| MSSO | Metered Sub System Operator
| Others |
| MSSO | Minesite Scholarship Screening Office
| Others |
| MSSO | Mission Support Services Office
| Others |
| MSSO | Mlo And Sliding Springs Observatory
| Others |
| MSSO | Mobile Single Sign On
| Others |
| MSSO | Moores School Symphony Orchestra
| Others |
| MSSO | Moscow State Symphony Orchestra
| Others |
| MSSO | Multi Sun Synchronous Orbits
| Others |
| MSSO | Multicultural Student Services Organization
| Others |
| MSSO | Multiple Source Simple Output
| Others |
| MSSO | Museum Studies Student Organization
| Others |
| MSSO | Muslim Student Society Officer
| Others |