aa
1 of 4noun (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
Kendrick FrazierAa 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
Science NewsThe 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 Gemma Tarlachaa
2 of 4abbreviation (1)
ana
AA
3 of 4noun (2)
ˈdə-bəl-ˈā
plural AAs
: aa battery
AA
4 of 4abbreviation (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
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 2abbreviation
1
achievement age
2
Alcoholics Anonymous
3
arachidonic acid