on c - orga
- operator's console
- operator's desk
- opportunity airfield
- opposed jet combustion chamber
- opposing
- opposing block protection
- opposing party
- opposing series connection
- opposing train
- opposite elevation
- opposite propellant
- opposite tank
- optic measurement
- optical angle
- optical automatic ranger
- optical axis
- optical beacon
- optical carrier
- optical communication
- optical communication receiver
- optical communication system
- optical computer
- optical data
- optical data processing
- optical decoy
- optical density
- optical direction and ranging
- optical doppler radar
- optical electronic digital logic
- optical electronic sight
- optical equipment
- optical filter
- optical frequency
- optical guidance system
- optical haze
- optical head
- optical homer
- optical homing
- optical homing device
- optical inertial guidance and navigation system
