an adjective used to describe an attractive woman. A play on the word "hot" pronounced with a long "a" like in the words apple, bat, alto, etc. hold the "aaa" out long and change pitches from low to high
"Holy shit, have you seen Kelly Smith lately? She's been wearing mini skirts every day in English!"
"Oh, I've noticed. She's haaat! I'd tap that anyday."
"Same here dude. Nobody in our school is as haaat as she is."