aa

1 of 4

noun (1)

ˈä-ˌä 

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

AA

3 of 4

noun (2)

ˈdə-bəl-ˈā 

plural AAs

: aa battery

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

Phrases Containing aa

• AA battery
• AA cell

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

achievement age

2

Alcoholics Anonymous

3

arachidonic acid

Etymology

Abbreviation

Latin ana