There are 2 main definitions of aa in English:


Syllabification: aa
Pronunciation: /ˈäˌä


Basaltic lava forming very rough jagged masses with a light frothy texture. Often contrasted with pahoehoe.
More example sentences
  • Roads of black ash traverse it, winding through the otherwise untraversable aa.
  • A serpentine flow meanders through formations of smooth pahoehoe lava and rough aa lava, the same forms common in basalt lavas.
  • Very different from jagged aa, pahoehoe is the other general texture of newly solidified lava.


mid 19th century: from Hawaiiana-'a.

Definition of aa in: