noun
aa
AH-ah
noun
1
A type of volcanic lava that cools into a rough, jagged, broken-up surface, as opposed to smooth pahoehoe lava.
"The hikers wore thick boots to cross the sharp aa field near the crater."
How to Use Aa
Learner’s notesIn plain EnglishA geology term for chunky, jagged lava rock, most famously seen in Hawaii.
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The hikers wore thick boots to cross the sharp _____ field near the crater.
Etymology
Borrowed from Hawaiian ʻaʻā, describing this rough type of solidified lava.