| Abbreviation | Definition |
|---|---|
| IPSX | Midwest Energy Services (GATX) |
| IPSZ | Indiana Public Service Commission |
| IPWX | Interstate Power (Alliant Energy) |
| IPWX | Interstate Power Company |
| IPWZ | IP Wood |
| IPXU | Seacube Container Leasing |
| IPZ | Intalco Plant |
| IQIX | Industria Quimica Del letmo de CV |
| IR | Illinois RailNet |
| IR | Illinois RailNet Incorporated |
| IR | Indian Railway |
| IRAP | Industrial Rail Access Program |
| IRCC | Inverness Railway and Coal Company |
| IRCTC | Indian Railway Catering and Tourism and Corporation |
| IREX | IRECO |
| IREX | IRECO Incorporated |
| IRHB | Iron Range and Huron Bay Railroad |
| IRHX | Iron Horse Railroad |
| IRIMEE | Indian Railway Institute of Mechanical and Electrical Engineering |
| IRIMEE | Indian Railway Institute of Mechanical and Electrical Engineers |