Fart Residue 

residue built up from repeatedly farting on any type of object consisting of fabric (clothes, seats, blankets, etc) this leaves a heavy scent of fart in the affected areas

After eating Indian food, I had a massive amount of fart residue in my boxers

Fart Residue by hardhitr3 December 7, 2009

Fart Residue 

The soaked in, gelatinous remains on your underwear after a very hot and wet fart.

Aw man, I got fart residue on my underpants.

Fart Residue by MrThatMan November 12, 2017