The Collaborative International Dictionary of English v.0.48:

AA \AA\ n.
   1. acronym for Associate in Arts, a college degree granted
      for successful completion of a two-year course of study in
      arts or general topics.

   Syn: Associate in Arts
        [WordNet 1.5]

   2. Alcoholics Anonymous. [Acronym.]
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

aa
    n 1: a dry form of lava resembling clinkers
    2: an international organization that provides a support group
       for persons trying to overcome alcoholism [syn: Alcoholics
       Anonymous, AA]
    3: an associate degree in arts [syn: Associate in Arts, AA]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

AA
       Auto Answer (MODEM)