Once again tsuwm has a wwftd worth a bit of further discussion.

AA is a kind of lava that is fragmented into small sharp prisms that hurt your bare feet so that you say "A! A!" as you gingerly pussyfoot across it.

Pahoehoe is the more common lava that has a relatively smooth surface.

For a discussion of them, here is a URL with some excellent pictures and description:

http://volcano.und.nodak.edu/vwdocs/vwlessons/lava.html

Dear Jackie: I cannot remove offensive word from heading in your post or in your text.

Dear Dr. Bill,

I have read about this type of lava. One time, I went to hear a Louisville native speak about having participated in his first Iron Man triathlon, and it had been in Hawaii.
He said he'd been told to make special preparations for the run across lava, because of the unusual conditions therein, one being no shade or any plant life to mitigate the sun's heat.
Could I ask you a favor, please sir? In view of the extremely high sensitivity at this time, would you mind replacing the word hijack in your subject title with something else? Thank you for reading this, at least. Love.

Aaaaaaaa!

Here is another site with an article about "aa". http://phrontistery.50megs.com/disq1.html

Which is the Australian spelling of "beer", isn't it? Or are there too many X's? Could mean more than one bottle, of course.

- A Zilder in Pommyland

Dear Faldage: A soul rising on its way to heaven met a bird, and said:"Ah, bird!" The bird replied "Ah! soul!"

"aa" is more properly written with an okina to show there is a glottal stop. - a'a.
And in case you're having a problem with pahoehoe : it is pronounced Pah-hoy-hoy like the hoy in Ahoy.
Pahoehoe is smooth and, like a'a, black and retains the heat of that tropic sun! Some people turn back from treks because the heat coming up through even the thick soles of walking/running sneakers is too much for them.
A'a can cut the soles of even very sturdy shoes all to heck so if you're planning a walk ... *don't *go *barefoot!

Webster's Encyclopedic Unabridged Dictionary of the English Language (1989)

Brilliant Wordwind. Now that you have mentioned it I know it will pop into my mind when I desperately need it in Scrabble.

>So where's the dictionary that includes a'a as aa so we can use it in Scrabble?

that would be the OSPD (official scrabble® players dictionary) -- it's the very first word therein. :-)

So where's the dictionary that includes a'a as aa so we can use it in Scrabble?

Good question to aask, Wordwind. Welcome aBoard, neighbor! I love your name, by the way! You sound really neat, and I bet we'll all be glad you joined us.