| Occupational Training Center | Academic & Science |
| Ogeechee Technical College | Academic & Science |
| Bol | Airport Code |
| Over the Counter | Banking |
| Osaka Titanium Technologies | Business |
| Ortac Resources, LTD. | Business |
| Open Text Corporation | Business |
| Otoc Limited | Business |
| Open Text Corp | Business |
| Owatonna Tool Company | Business |
| Operation and Transport Corporation | Business |
| On Target Commission | Business |
| OnTrack Consulting | Business |
| Online Travel Company | Business |
| Outside Threaded Container | Business |
| Open Tubular Column | Chemistry |
| Offshore Technology Conference | Community |
| Ozarks Technical Community | Community |
| Outreach Throughout the Community | Community |
| One True Church | Community |
| Our Time Cabaret | Community |
| Original Trilogy Collection | Community |
| One Team Conference | Community |
| Olney Theatre Center | Community |
| Overflow of Tacho Counter | Computer Assembly Language |
| Offshore Technology Conferences | Computing |
| Operations Technical Center | Computing |
| Over The Cell | Computing |
| Optimization Technology Center | Computing |
| Ohio Technical College | Educational Institute |
| Okefenokee Technical College | Educational Institute |
| Output Transformer Coupled | Electronics |
| Ozone Transport Commission | General |
| On the Counter | General |
| On The Con | General |
| Open Transparent and Connected | General |
| Oh Those Clowns | General |
| Order Through Chaos | General |
| On The Cool | General |
| Orbiter Test Conductors | General |
| Off The Chart(s) | General |
| Online Training Center | General |
| Ocean Thematic Centre | General |
| Oldtimer Center | General |
| Other Than Collision | General |
| On The Car | General |
| Overhead Trip Computer | General |
| Oklahoma Truck Club | General |
| Ontario Triumph Club | General |
| Oldtimer Club | General |
| Ohio Transportation Consortium | General |
| Original Teile Center | General |
| Other Than Clinton | General |
| Ocean Systems Technician Chief Petty Officer | Governmental |
| Overseas Telecommunications Commission | Governmental |
| Officers Training Conference | Governmental |
| Oklahoma Tax Commission | Governmental |
| Oregon Transportation Commission | Governmental |
| Offender Time Computation | Governmental |
| Online Teen Club | Internet |
| Ornithine Transcarbamylase | Medical |
| Ornithine Transcarbamylase Deficiency | Medical |
| Off Topic Comments | Messaging |
| Operational Test Command | Military and Defence |
| Officer Training Corps | Military and Defence |
| Officer In Tactical Command | Military and Defence |
| On-going Test Case | Softwares |
| Orbiter Test Conductor | Space Science |
| Other Tennis Club | Sports |
| Olympic Training Center | Sports |
| On The Clock | Sports |
| Optical Telephone Corporation | Stock Exchange |
| Office of Technology Commercialization | Technology |
| One-time Charge | Telecommunication |
| Operating Telephone Company | Telecommunication |
