| O.T.R. | Occupational Therapist Registered 
| Others |
| OTR | Oakland Terminal Railway
| Others |
| OTR | Occupational Therapist Rehabilitation
| Others |
| OTR | Occupational Therapist, Registered
| Others |
| OTR | Oceanic Transition Route
| Others |
| OTR | Odyssey Touring
| Others |
| OTR | Off The Rack
| Others |
| OTR | Off The Record
| Others |
| OTR | Off The Road
| Others |
| OTR | Office of Tax and Revenue
| Others |
| OTR | Office Of Technology Resources
| Others |
| OTR | Old Time Radio
| Others |
| OTR | Old Timers Reunion
| Others |
| OTR | Omologato Turismo Radiale
| Others |
| OTR | On Target Reports
| Others |
| OTR | On The Rag
| Others |
| OTR | On The Record
| Others |
| OTR | On The Rocks
| Others |
| OTR | On The Run
| Others |
| OTR | On Time Reporting
| Others |
| OTR | One Time Registration
| Education, Event, Exhibition, Meetings and Conferences, Program, Project |
| OTR | One Time Repair
| Others |
| OTR | One Touch Record
| Others |
| OTR | One Touch Recording
| Others |
| OTR | One True Ring
| Others |
| OTR | Operating Temperature Range
| Others |
| OTR | Operating Time Record
| Others |
| OTR | Operational Test Requirement
| Others |
| OTR | Operational Trouble Report
| Others |
| OTR | Operational Turn Around
| Business, Military, Weapon |
| OTR | Optical Transceiver
| Others |
| OTR | Oral Tradition Room
| Others |
| OTR | Order To Receipt
| Others |
| OTR | Orientation Transition and Retention
| Others |
| OTR | Oscillatory Transition Return
| Others |
| OTR | Other Terrestrial Radio
| Others |
| OTR | Output Routine
| Others |
| OTR | Oval Track Racer
| Others |
| OTR | Oval Track Racing
| Others |
| OTR | Over The Rainbow
| Others |
| OTR | Over The Rhine
| Others |
| OTR | Over The Road
| Others |
| OTR | Over-the-Rhine
| Others |
| OTR | Over-The-Road container
| Others |
| OTR | Own The Room
| Others |
| OTR | Oxygen Transfer Rate
| Others |
| OTR | Registered Occupational Therapist
| Others |