Defining "hooah"

The AP has a cool article today about "hooah".

They shout hooah to get motivated, and they whisper it when they concur with something someone just said. Hooah means you understood something, or is the proper reply when someone says "thank you." On the other hand, it may also be used to say "thank you."

Hooah is a catchall phrase that will get you out of any situation, particularly when receiving a scolding from a higher-ranking officer.

"You use it when you've got a flame on your butt and you're just trying to extinguish it," said Capt. Brian Buckner, 30, of Sumter, S.C.

Take this conversation, overheard recently outside the mess hall at Camp Rustamiyah, on Baghdad's eastern outskirts:

Soldier 1: How you doing?

Soldier 2: Fine. How you doing?

Soldier 1: Hooah.

This is one of those words where you just kind of know what it means, and you can't quite define it :>