A state of complete insanity, going off the deep end.
The grandmother of all hissy fits - totally off the heezy.
Jeez, all I said was that those pants made your butt look big - you don't have to go all whipshit on me !
Usually preceded by "you are the", a title of praise for someone who has done something extraordinary. Functions identically to a host of other congratulatory expressions, such as "you kick ass," "you're the Man," "You're a champ," etc.
You finished the project three weeks early? You are the whipshit!