Derived from the word
portmanteau, which is when 2 different words are joined to create another word (e.g.
fantabulous, which is the combination of fantastic & fabulous), fartmanteau is when the made-up word falls under
toilet humor .
Dude 1: Duuuuude, I thought up
another word today while smoking out. Shitarded. It's when
something is both shitty & retarded.
Dude 2:
That's dope.
Dude 1: No...That's a fartmanteau, my friend.