What is Ain't It?
A termed of agreement used most commonly in the Gary-Chicago arean be used to replace "hell yeah" and other positive affirmations. Short for "ain't it the truth"
This weed is the shit!
A relatively new interrogative phrase, independent of the preceding verb tenses, used to emphasize the extreme nature of the preceding clause.
The phrase has its origins in the Atlanta Public School System. In its most common incarnation, it's said with a humorous, yet sassy look over one's glasses, or general "girlfrand!" attitude.
(You mad, ain't it?!?!)
(You ain't mad, is it!?!)