| Abbreviation | Definition |
|---|---|
| IRC | Inland Revenue Commissioner |
| IRC | Irish Republican Constabulary |
| IRLJ | Infraction Rules for Courts of Limited Jurisdiction |
| IRM | Department of Commerce -- Information Resource Management Division |
| IRMC | Information Resource Management Commission |
| IRP | Investigative Review Panel |
| IRT | Incident Response Team |
| IRU | Indefeasible Right of Use |
| ISAOA | Its Successors And/Or Assigns |
| ISB | Idaho State Bar |
| ISB | Illinois State Bar |
| ISB | Indiana State Bar |
| ISB | Iowa State Bar |
| ISBA | Illinois State Bar Association |
| ISBA | Indiana State Bar Association |
| ISBA | Iowa State Bar Association |
| ISC | International Supreme Council |
| ISO | International Standards of Operations |
| ISR | Illegal Street Racer |
| ISR | Illegal Street Racing |