Also:

• AA is a size of battery ("double A")
• AA and A.A. are abbreviations for Alcoholics Anonymous , antiaircraft (also A-A and A.-A.), automobile association , and Associate of (or in) Arts .

English

Pronunciation

• ä'ä, /ˈɑːɑː/, /"A:A:/

Etymology

Hawaiian ʻaʻā

Noun

aa

1. A type of basaltic rock, usually dark-colored with a jagged surface, formed in large sheets from slow-moving lava. It is one of two chief forms of rock emitted from volcanoes of the Hawaiian type, the other being pahoehoe.

   Quotations

   • 1859 - R. C. Haskell in American journal of science and arts, series XXVIII

     We...saw 'pahoihoi' or solid lava forming, and also 'aa' or clinkers.

   • 1883 - Clarence E. Dutton in the fourth Annual report of the United States Geological Survey

     The second form of the lavas is called by the natives a-a, and its contrast with pahoehoe is about the greatest imaginable. It consists mainly of clinkers sometimes detached, sometimes partially agglutinated together with a bristling array of sharp, jagged, angular fragments.

   • 1944 - Charles A. Cotton: Volcanoes as landscape forms

     Cooling and solidification frequently takes a different course...in lava flows, producing the clinker-like 'aa' lava.

Translations

• Estonian: aa-laava
• Hawaiian: ʻaʻā

Estonian

Interjection

aa

1. Expresses recognition. Aa, see oled sina. Oh, it's you.
2. Expresses understanding. Aa, saan aru. Oh, I understand.