Depending on context this can mean either something, or someone who is:
1) Way [far out] there; extremely [fucked up]; an idiot OR,
2) beyond greatness; [supercool]; [the bomb]; very sexy.
> EXAMPLE 1
> "Here comes that dumbass, [Dice'n Tyson]. Man, he is [MADWHACK off the track]!"
> EXAMPLE 2
> "Yo, dawg, check it out. This station's playin' some MADWHACK [remix] [beats] tonight.