Fartox is an insult that you call someone who farted
Person 1: eeeewwww do u smell that??
Person 2: yea it came from that fartox over there
The worst and most foul smelling fart. Also can be used as a descriptive term for something unpleasant.
Biff: "Watch out that one was fartoxic"
Jeb: *dies*
also
Zep: "Check out my ride, it is totally bitchn."
Harpo: "That thing is fartoxic bro, definitely not gonna chase any tail tonight."
Zep: *frown*