| Abbreviation | Definition |
|---|---|
| ICRX | Island Creek Corporation |
| ICRZ | Illinois Central Railroad (Canadian National Railway) |
| ICRZ | Illinois Central Railroad Company |
| ICSU | TAL International |
| ICSU | Transamerica Leasing Incorporated |
| ICSZ | TAL International (Union Pacific Railroad) |
| ICSZ | Transamerica Leasing Incorporated (formerly ICS Industries) |
| ICUU | Independent Container Line |
| ICYQ | Intermet - Columbus Foundry |
| ICZ | IPS Company |
| IDAC | Idaho Central Railroad (Boise Pacific Railroad) |
| IDAX | Industria del Alcali |
| IDCC | Ideal Cement Company |
| IDCU | Ideal Container |
| IDCZ | Industrial Development Co-op Clinton County |
| IDEZ | Independent Explosive |
| IDOX | Lockheed Idaho Technologies Company |
| IDOX | United States Department of Energy Idaho Operations Office |
| IDSZ | Industrial Distribution Service |
| IDSZ | Industrial Distribution Service Incorporated |