| Abbreviation | Definition |
|---|---|
| ATSC | Analog Television Systems Corporation |
| ATSI | Advance Technical Solutions Inc |
| ATSI | Ahtna Technical Services Inc |
| ATSI | American Technical Solutions Inc |
| ATSI | American Transcription Solutions Inc |
| ATSI | Applied Thermal Systems Inc |
| ATSI | Athens Technical Specialists INC |
| ATSO | Affordable Translation Services Ottawa |
| ATT | Aakash Television Tutoring |
| ATT | American Telephone and Telegraph, Inc. (AT&T) |
| ATTB | All The Top Bananas |
| ATTC | American Torch Tip Company |
| ATTC | American Tug and Transit Company |
| ATTF | All Things That Fly |
| ATTG | Aisin Takaoka Thailand Group |
| ATTL | Aishwarya Technologies and Telecom Ltd |
| ATTL | Applied Textile Technologies Ltd |
| ATTOMS | Alabama Terrorism & Tactical Operations Medical Support, L.L.C. |
| ATWC | Arizona Two Way Communications |
| ATWC | Around The World Cruises |