aa (uncountable)

  1. A form of lava flow of basaltic rock, usually dark-colored with a jagged and loose, clinkery surface. It is one of two chief forms of lava flow emitted from volcanoes of the Hawaiian type, the other form being pahoehoe.
    • 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.

2 letters in word "aa": A A.

No anagrams for aa found in this word list.

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