Initialism of acetic acid. / Initialism of acting age. / (medicine) Initialism of alveolar-arterial. / Initialism of aminoacetone. / Initialism of amino acid. / Initialism of approximate absolute.

Abbreviation of ana (“of each, equal parts”).

Initialism of arctic-alpine. / Initialism of always afloat.

Abbreviation of adjectives. / Abbreviation of arteries.

(volcanology) A form of lava flow associated with Hawaiian-type volcanoes, consisting of basaltic rock, usually dark-colored with a jagged and loose, clinkery surface. Compare pahoehoe.

Initialism of Alcoholics Anonymous; also A.A.: a self-supporting organization of alcoholic people.

(computer graphics, transitive) To antialias.

(military, aviation) Initialism of anti-aircraft and anti-air; also a/a, A-A, A/A. / (military, aviation) Initialism of air-to-air. / (anatomy, medicine) Initialism of atlantoaxial.

A member of Alcoholics Anonymous. / An AA battery (energy-storage device). / Initialism of affirmative action. / Initialism of air armament. / Initialism of air attaché.

(military) Initialism of armor, armament, and ammunition.