What does OMSA stand for?

Offshore Marine Service Association - New Orleans, LA (EA)

Ohio Middle School Association (EARSL)

Ontario Medical Secretaries Association (SAUS)

Orders and Medals Society of America (EA)

Ordnance Missile Support Agency (SAA)

Otitis Media, Suppurative, Acute - Medicine

Seaman Apprentice, Opticalman, Striker - Navy rating

Simcoe County Archives, Minesing, Ontario - Library symbol - National Library of Canada (NLC)