aa

1 of 4

noun (1)

ˈä-ˌä How to pronounce aa (audio)
ä-ˈä
variants or a'a
geology
: basaltic lava having a rough, broken surface
This jumble of two-year-old black rock is of the type known as aa (pronounced ah-ah). This is the term borrowed from the Hawaiian language for lava that is broken, jagged and angular, in contrast to the smooth or rope-textured pahoehoe …Kendrick Frazier
Aa is formed from stiffer, more viscous lava with a thick brittle crust that becomes broken and heaped up as it is carried along by the molten lava beneath.Science News
The same eruption of lava can switch from pahoehoe to a'a, depending on factors such as thickness and how fast it's cooling.Gemma Tarlach
compare pahoehoe

aa

2 of 4

abbreviation (1)

ana
plural AAs

AA

4 of 4

abbreviation (2)

1
administrative assistant
2
Alcoholics Anonymous
3
antiaircraft
4
arachidonic acid
5
associate in arts
6
author's alterations

Word History

Etymology

Noun (1)

borrowed from Hawaiian 'a'ā "to burn, lava with a broken surface, abounding in such lava"

First Known Use

Noun (1)

1859, in the meaning defined above

Noun (2)

1937, in the meaning defined above

Time Traveler
The first known use of aa was in 1859

Dictionary Entries Near aa

Cite this Entry

“Aa.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/aa. Accessed 25 Feb. 2024.

Medical Definition

āā

1 of 2 abbreviation
variants also aa
of each
used at the end of a list of two or more substances in a prescription to indicate that equal quantities of each are to be taken

AA

2 of 2 abbreviation
1
2
Alcoholics Anonymous
3
Etymology

Abbreviation

Latin ana

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