| Abbreviation | Definition |
|---|---|
| CLCZ | Complete Logistics Company |
| CLDZ | Celadon Trucking Services |
| CLDZ | Celadon Trucking ServicesIncorporated |
| CLEX | Chemical Enterprises (Cieco Corporation) |
| CLGR | Central Louisiana and Gulf Railroad |
| CLGU | Costa Line Cargo Services |
| CLHU | Capital Intermodal Services |
| CLHU | Capital Intermodal Services Ltd |
| CLIC | Car Location and Inventory Control |
| CLIF | Cliffside Railroad |
| CLIX | Calumet Lubricants |
| CLK | Cadillac and Lake City Railway |
| CLMX | Consolidated Thompson Iron Mines Limited |
| CLMX | Cyprus Sierrita Corporation |
| CLNA | Carolina Coastal Railway |
| CLNA | Carolina Coastal Railway Incorporated |
| CLOU | CLOU Container Leasing |
| CLOU | CLOU Container Leasing GMBH |
| CLOX | Clark Refining and Marketing |
| CLP | Clarendon and Pittsford Railroad |