Orbiter Access Arm 
Orbiter Alternate Airfield 
Open Agent Architecture 
Office of the Assistant Administrator 
Old Age Assistance 
office administrative assistant 
Office of Academic Affairs 
Older Americans Act 
Open Avionics Architecture 
Observatorio Astronómica de Argentina 
Obstetric Anaesthetists' Association 
Office of Academic Affiliations 
Office of Assessment & Accountability 
oleic acid anilide 
On Air Activation 
Ontario Association of Architects 
Ontario Automobiel Association 
Ontario Automobile Association 
Open Arcade Architecture 
Operational Assessment Analysis 
opportunity-available action 
Opticians Association of America 
Orient Airlines Association 
Oriental Astronomical Association 
Outdoor Advertising Association 
Over Air Addressing 
Owners Association Alliance 
Oxalacetate 
oxalacetic acid 
Oxalic Acid Anodizing