| Acronym | Definition |
|---|
| TIR | Total Internal Reflection |
| TIR | Thermal Infrared (ASPRS) |
| TIR | Tasa Interna de Retorno (Spanish: Internal rate of return) |
| TIR | Toll-Interleukin 1 Receptor |
| TIR | Traumatic Incident Reduction |
| TIR | Technical Information Release (IRS) |
| TIR | Total Indicator Reading |
| TIR | Total Indicated Runout |
| TIR | Technical Information Report |
| TIR | Total Indicator Runout |
| TIR | Translation Initiation Region |
| TIR | Transit International Routier |
| TIR | Total Item Record |
| TIR | Transport International de Marchandises par Route (French: international cariage of goods by rail) |
| TIR | Transport International par la Route (French) |
| TIR | Test Incident Report |
| TIR | Total Internal Refraction |
| TIR | Time in Rate (pay grade) |
| TIR | Texas Independence Relay |
| TIR | Target Illuminating Radar |
| TIR | Terminal Imaging Radar |
| TIR | Transport International de Marchandises par la Route |
| TIR | The Internet Ramp (Michigan ISP) |
| TIR | Type Inspection Report |
| TIR | Transport Internationaux Routiers |
| TIR | Target Impulse Response |
| TIR | True Image Recovery (Veritas Netbackup) |
| TIR | Trailer Interchange Receipt |
| TIR | The Inspiration Room (website) |
| TIR | Test Inspection Report |
| TIR | Technology Insertion Recapitalization |
| TIR | Tactical Intelligence, Reconnaissance |
| TIR | Technical Infrastructure Requirements |
| TIR | Technical Interface Requirement |
| TIR | Technical Interoperability Requirement |
| TIR | Technical Interface Recertification |
| TIR | Target Individual Risk |
| TIR | Team Impulse Racing |
| TIR | Total Incidents Recorded (safety statistics) |
| TIR | Trainee Integrated Ratings |
| TIR | Trouble Incident Report |
| TIR | Test-In Reliability |
| TIR | Tie in Requirements |
| TIR | Transaction Item Record/Report |
| TIR | Trip Indication Relay (circuitry) |