noun
Common
aa
AH-ah
Aa (noun) means a type of volcanic lava that cools into a rough, jagged, broken-up surface, as opposed to smooth pahoehoe lava. Example: “Walking barefoot on aa lava is painful because it is so sharp.”
noun
1
A type of volcanic lava that cools into a rough, jagged, broken-up surface, as opposed to smooth pahoehoe lava.
"Walking barefoot on aa lava is painful because it is so sharp."
"Unlike smooth pahoehoe, aa breaks into rough clinkers that crunch underfoot."
"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.
Vocabulary Flow
Build your vocabulary from words like aa.
Vocabulary Flow serves the next word, and the next — meaning, pronunciation and an example each time. Practice at your level, or learn English in your own language.
Start vocabulary practice
Fill the gap
Can you complete this real example?
Walking barefoot on _____ lava is painful because it is so sharp.
Etymology
Borrowed from Hawaiian ʻaʻā, describing this rough type of solidified lava.
Rhymes for aa
See all rhymes for aa →Frequently asked questions
What does “aa” mean?
The word “aa” means a type of volcanic lava that cools into a rough, jagged, broken-up surface, as opposed to smooth pahoehoe lava. In plain terms, a geology term for chunky, jagged lava rock, most famously seen in Hawaii.
How do you pronounce “aa”?
“Aa” is pronounced AH-ah (/ˈɑ.ɑ/ in IPA).
How do you use “aa” in a sentence?
Here is “aa” used in a sentence: “The hikers wore thick boots to cross the sharp aa field near the crater.”
What part of speech is “aa”?
“Aa” is a noun.
Is “aa” a common word?
“Aa” is a fairly common word in modern English.
What is the difference between aa and pahoehoe lava?
Aa is lava that cools into a rough, jagged, broken-up surface, while pahoehoe cools smooth and often ropy-looking. The two can come from the same volcano and even the same eruption; the contrast lies in how the lava behaves as it flows and cools, not in its chemical makeup.
Is aa a valid word in Scrabble?
Yes. Aa is accepted in the major Scrabble word lists used in both North American and international play, which makes it one of the most useful two-letter words in the game. It scores only two points on its own but is prized for fitting into tight corners of the board.
Where does the word aa come from?
Aa was borrowed from Hawaiian, where the word describes exactly this rough, clinkery type of lava; its companion term pahoehoe is Hawaiian as well. Geologists adopted both words as standard terms because Hawaii's volcanoes display the two lava types so clearly.
Why does lava become aa instead of pahoehoe?
Lava tends to form aa when it is cooler, stiffer, or losing gas quickly, causing the surface to tear into jagged, broken blocks. Hotter, more fluid lava spreads gently and skins over into smooth pahoehoe. A single flow can start as pahoehoe and change into aa as it cools and thickens downslope.
Featured in
Vocabulary lists that include aa:
