AT

1.  @ (or "at sign")
2. Aarne-Thompson classification system
3. Acceptance test
4. Ampere-turn 
5. Anaerobic threshold
6. Análisis transaccional
7. Anti-tank 
8. Antithrombin
9. Appalachian Trail
10. Appropriate technology
11. Archive Team
12. Ashmore and Cartier Islands 
13. Assistive technology
14. Astatine
15. at (Unix)
16. at (Windows)
17. AT form factor 
18. At, Bihar
19. Ataxia telangiectasia
20. Atchison County, Kansas 
21. Attotesla
22. Austria's
23. Automatic transmission
24. Aviation Electronics Technician
25. Province of Asti
26. Royal Air Maroc
27. Technical atmosphere