| Abbreviation | Definition |
|---|---|
| ATIA | Aruba Trade Industry Association |
| ATIF | Association of Translators and Interpreters of Florida |
| ATIM | Association of Translators and Interpreters of Manitoba |
| ATIS | Association of Translators and Interpreters of Saskatchewan |
| ATJ | Association of Teachers of Japanese |
| ATLA | Arkansas Trial Lawyers Association |
| ATMA | American Tibetan Mastiff Association |
| ATMA | Association of Technical Market Analysts |
| ATMNYC | Association of the Teachers of Mathematics of New York City |
| ATNA | Argay Terrace Neighborhood Association |
| ATOA | Alabama Tactical Officers Association |
| ATOA | Arizona Tactical Officers Association |
| ATOA | Arkansas Tactical Officers Association |
| ATOR | Association of TourOper of Russia |
| ATP | Association for the Tutoring Profession |
| ATP | Association of Test Publishers |
| ATPA | Addiction Treatment Providers Association |
| ATPA | Alabama Transportation Planners Association |
| ATPA | Arkansas Timber Producers Association |
| ATPO | Association of Technical Personnel in Ophthalmology |