| Center for Science Outreach | Academic & Science |
| Central Statistics Ofice | Academic & Science |
| Campus Service Officer | Academic & Science |
| Campus Safety Officers | Academic & Science |
| Chartered Student Organizations | Academic & Science |
| Correct Solutions Only | Academic & Science |
| Civil Society Organisations | Academic & Science |
| Central Statistic Office | Academic & Science |
| Magdeburg | Airport Code |
| Canberra Symphony Orchestra | Arts |
| Christchurch Symphony Orchestra | Arts |
| Columbia Symphony Orchestra | Arts |
| Central Statistical Organisation | Banking |
| Chief Sales Officer | Business |
| Career Services Office | Business |
| Coated Side Out | Business |
| Construction Safety Officer | Business |
| Career Services Online | Business |
| Chief Services Officer | Business |
| Chief Sustainability Officer | Business |
| Correct Solution Only | Chemistry |
| Cleveland Symphony Orchestra | Community |
| Community Service Officer | Community |
| Chicago Symphony Orchestra | Community |
| Charleston Symphony Orchestra | Community |
| Colorado Symphony Orchestra | Community |
| Columbus Symphony Orchestra | Community |
| Community Service Officers | Community |
| Civil society organizations | Community |
| Community Snow Observations | Community |
| Charter Schools Office | Community |
| Christian Science Organizations | Community |
| Color Separation Overlay | Community |
| Community School Organization | Community |
| Combined Sewer Overflow | Community |
| Christian Science Organization | Community |
| Community Services Office | Community |
| Community Service Organization | Community |
| Chattanooga Symphony Orchestra | Community |
| Club Safeguarding Officer | Community |
| Charlotte Symphony Orchestra | Community |
| Community Service Order | Community |
| Community Services Offices | Community |
| Community Services of Oakland County, Michigan | Community |
| Community Services of Oakland | Community |
| Cincinnati Symphony Orchestra | Community |
| Community Support Officer | Community |
| Citizen Support Organization | Community |
| Central Student Outreach | Community |
| Civil Society Organisation | Community |
| Civil Society Organization | Community |
| Curvature of the Second Order | Computer and Networking |
| Computer Service Organization | Computing |
| Cognizant Security Office | Computing |
| Computing Services Office | Computing |
| Composite Second Order Beat | Computing |
| Cluster Supporting Object | Computing |
| Customer Solutions Online | Computing |
| C Shared Object | Computing |
| Chief Security Officer | Computing |
| Cyber Security Operations | Computing |
| Cloud Service Offering | Computing |
| Counter-Strike Online | Computing |
| Computer Systems Operation | Computing |
| Compressed Iso File | File Type |
| Coastal States Organization | General |
| Caltech Submillimeter Observatory | General |
| Combined Sewer Overflows | General |
| Common Scientific Outline | General |
| Content Standards and Objectives | General |
| Contour Segmentation Objects | General |
| Credit Services Organization | General |
| Combined Sewage Overflow | General |
| Customer Support Organization | General |
| Central Services Organization | General |
| Chief Sustainability Officers | General |
| Commercial Solutions Opening | General |
| Central Susquehanna Opportunities | General |
| Components and Supply Operations | General |
| Credit Services Organizations | General |
| Conflict and Stabilization Operations | General |
| Combined Sewer Outflow | General |
| Customer Service Officers | General |
| Customer Service Order | General |
| Celebrity Scratch Off | General |
| Customer Service Operations | General |
| Car Seal Open | General |
| Commercial Stakeholder Organisation | General |
| Cylinder Shut Off | General |
| Car Seat Only | General |
| Car Sales Organizer | General |
| Car Software Organisation | General |
| Chief Scapegoat Officer | General |
| Customer Service Officer | General |
| Collaboration Support Office | General |
| Cycles since Overhaul | General |
| Chief Stress Officer | General |
| Colour Separation Overlay | General |
| Contract Standing Order | Governmental |
| Central Statistical Office | Governmental |
| Central Statistics Office | Governmental |
| Court Services Officer | Governmental |
| Council for Student Organizations | Governmental |
| Combat Systems Officers | Governmental |
| Central Statistics Organization | Governmental |
| Czech Statistical Office | Governmental |
| Combat Systems Officer | Governmental |
| Court Security Officer | Governmental |
| Chief Scientist Office | Governmental |
| Commissioners Standard Ordinary | Governmental |
| Colonial Secretary's Office | Governmental |
| Court Service Online | Governmental |
| Chief Signal Officer | Governmental |
| Casetrack Support Officer | Governmental |
| Confederación Sindical Obrera | International |
| Cumhurbaskanligi Senfoni Orkestrasi | International |
| Consumer Safety Officer | Jobs |
| Chief Scientific Officer | Jobs |
| Customer Support Officer | Jobs |
| Customer Services Officer | Jobs |
| Common Source Outbreak | Medical |
| Community Service Office | Medical |
| Clinical Support Options | Medical |
| College of Syntonic Optometry | Medical |
| Clinical and Support Options | Medical |
| Chlamydia Screening Office | Medical |
| Chief Strategy Officer | Messaging |
| Chief Safety Officer | Military and Defence |
| Center for Special Operations | Military and Defence |
| Communications Support Organization | Military and Defence |
| Closely-spaced Objects | Military and Defence |
| Communications Service Order | Military and Defence |
| Central States of Omaha | Regional |
| Computer Security Official | Space Science |
| Computer Security Officer | Space Science |
| Magdeburg–Cochstedt Airport | Transport & Travel |
