Definition from Wiktionary, the free dictionary
- (electronics) Metal Oxide Semiconductor
- (computing) Maintenance Operating System
- (computing) Mobile Operating System
- Member of the Opposite Sex
- (military) Military Occupational Specialty
- "I was a marine. My MOS was 0311," he said.
- (law enforcement) Member of the Service
- "We have an MOS down," the dispatcher said.