| C&O | Caffeine and Octane 
| Others |
| C/O | Call On (date)
| Others |
| c/o | care of
| Others |
| C/O | Carried Over
| Others |
| C/O | Change Over
| Others |
| C/O | ChangeOut
| Others |
| C/O | CheckOut
| Others |
| C/O | Complaining of
| Others |
| C/O | Complaints Of
| Others |
| C/O | Contamination/Overpressure
| Others |
| C/O | Corner Of
| Others |
| C/O | CutOff
| Others |
| c/o | in Care Of
| Others |
| CO | C oxidase
| Others |
| CO | Cabinet Office
| Others |
| CO | Camp Oven
| Others |
| CO | Canon
| Others |
| CO | capital out-turn
| Others |
| CO | Carbon Monoxide
| Others |
| CO | Cardiac Output
| Others |
| CO | Cargo Operations Directorate
| Others |
| CO | Carry Over
| Others |
| CO | Cash Officer
| Others |
| CO | Castor Oil
| Others |
| CO | Casualty Officer
| Others |
| CO | Center Off
| Others |
| CO | Central Object
| Others |
| CO | Central Office
| Others |
| CO | Central Operations
| Others |
| CO | Certified Operator
| Others |
| CO | Certified Orthotist
| Others |
| CO | Cervical Orthosis
| Others |
| CO | Chamber Orchestra
| Others |
| CO | Change Order
| Others |
| CO | Charge Off
| Others |
| CO | Check Out
| Others |
| CO | Checked Out
| Others |
| CO | Chesapeake and Ohio Railway (CSX Transportation)
| Others |
| CO | Chief Officer
| Others |
| CO | Childhood Onset
| Others |
| CO | Church of
| Others |
| CO | Circle Office
| Others |
| CO | Circle Officer
| Designation / Rank, Police |
| CO | City Ordinance
| Others |
| CO | Clean Out
| Others |
| CO | Cleanout
| Others |
| CO | Clockwork Orange
| Others |
| CO | Closed Orbits
| Others |
| CO | Co Operation
| Others |
| CO | Cobalt
| Element |
| CO | Coconut Oil
| Others |
| CO | Code of Obligations
| Others |
| CO | Colchester
| Others |
| CO | collagen
| Others |
| CO | Colloidal Oligo
| Others |
| CO | Colombia
| Country, TLD |
| co | Colombia (ccTLD)
| Others |
| CO | Colonial Office
| Others |
| CO | Colorado
| State |
| CO | Columbia Field Office
| Others |
| CO | Column Output
| Others |
| CO | Coming Over
| Others |
| CO | Commanding Officer
| Others |
| co | Commercial
| Others |
| CO | Commerial Office
| Others |
| CO | Commissioned Officer
| Others |
| CO | Commissioner's Office
| Others |
| CO | Commissioners Office
| Others |
| CO | Como (Provence)
| Others |
| CO | Companies Ordinance
| Others |
| CO | Company
| Business |
| CO | Compensatory Off
| Others |
| CO | Complains Of
| Others |
| CO | Complete Occlusion
| Others |
| CO | Compliance Officer
| Others |
| CO | Conditional Offer
| Others |
| CO | Conference Officer
| Others |
| CO | Connectors And Orientors
| Others |
| CO | Conscientious Objector
| Others |
| CO | Conscientious Objector (to war or whatever)
| Others |
| CO | Consolildated-Vultee, San Diego
| Others |
| CO | Continental Airlines
| Others |
| CO | Contract Officer
| Others |
| CO | Contracting Officer
| Others |
| CO | Contractual Obligation
| Others |
| CO | Controlling Office
| Others |
| CO | Convenience Outlet
| Others |
| CO | Cooking Officer
| Others |
| CO | Copyright Office
| Others |
| CO | Coronary Occlusion
| Others |
| CO | Corporate Office
| Others |
| CO | Correction Officer
| Others |
| CO | Corrections Officer
| Others |
| CO | Corrupted Organizations
| Others |
| CO | Corsican
| Others |
| CO | Country Office
| Business |
| CO | County
| Others |
| CO | Course Organiser
| Others |
| CO | Crematory Operator
| Others |
| CO | Cronym Or
| Others |
| CO | Cumulus Oophorus
| Others |
| CO | Current Offer
| Others |
| CO | Current Owner
| Others |
| CO | Customer Order
| Others |
| CO | Customization Operator
| Others |
| CO | Cut Off
| Others |
| CO | Cut out
| Others |
| CO | cyclooxygenase
| Others |
| CO | Cytochrome Oxidase
| Others |
| CO | The Creator Owner
| Others |
| Co. | Coral
| Others |