(idiomatic, informal) A combination of two factors or reasons.

(occult) A Thelemic spiritual organization founded in 1907 by British occultists Aleister Crowley and George Cecil Jones.

(medicine) Arterial to alveolar oxygen ratio.

Abbreviation of air-to-air.

(military) Initialism of antiaircraft.

(military) Initialism of antiaircraft.

Initialism of agnostics/atheists.

(astronomy, astrophysics) Initialism of Astronomy and Astrophysics: a scientific journal founded in 1969, covering theoretical, observational, and instrumental astronomy and astrophysics.

(physiology) Initialism of alveolar-arterial.

Abbreviation of Aid and Attendance (additional pension funding provided to certain United States war veterans)