The splattered oily residue left behind after a moist fart, often occuring after a very loose shit. This leads to Chad and might smear further until reaching the Taint or Gooch. Itching and burning may follow soon after, and even sooner after that, a skid mark will occur.
Girl: Dude, my taint is itching like MAD!
Girl2: What happened? Did your bike seat ride too high?
Girl: No, I had a pretty nasty fart before I got on my bike and I think it left a FART PASTE that's kinda spread around my ass and taint and now it itches!
To give someone's pokemon obscene or otherwise undesirable nicknames when he or she isn't watching.
From a series of incidents in which pokemon were renamed "fartpaste"
I left my gameboy at Steve's and he fartpasted my silver version something feirce.