| Abbreviation | Definition |
|---|---|
| COAL | ColdFusion Open Application Library |
| COCA | Corpus Of Contemporary American English |
| COLL | collated |
| Coll | Collection |
| coll. | collated |
| coll. | collation |
| Coll. | Collection |
| CompRendHebdom | Comptes Rendus Hebdomadaires des Seances, Academie des Sciences |
| CONMDL | Consolidated Message Distribution Library |
| CONSEC. | Consecutive |
| COOL | Clear Ongoing Open Library |
| COOL | Consortium of Ohio Libraries |
| COOL | Council Of Our Library |
| COOT | Oakland Tribune, Oakland, California, Library symbol |
| COOV | Ovid Public Library, Ovid, Colorado, Library symbol |
| COPL | Charter Oak Public Library |
| COSALC | Coalition of South African Library Consortia |
| COSEC | Consortium of Slovenian Electronic Collections |
| COSLA | Chief Officers of State Library Agencies |
| COSLA | Chief Offices of State Library Agencies |