AT or at may stand for:

• acceptance test
• AT form factor for motherboards and computer cases, in IBM PC
• aero triangulation
• alimentary tract
• anaerobic threshold
• anti-tank
• anti-terrorism (see also: counter-terrorism)
• Appalachian Trail
• assistive technology
• astatine (At), chemical symbol for the chemical element
• at
  • commercial at: the punctuation symbol "@", now principally used in e-mail addresses.
  • ATtention, part of the Hayes AT command set for modems
  • at (Unix command) to schedule tasks to be performed at a later date
  • technical atmosphere
• audit trail
• Austria (ISO 3166-1 alpha-2 country code)
• automatic transmission
• the IATA code for Royal Air Maroc
• The Old 5-pin connector used on ibm at computers

See also: wiktionary:at