pants blaster
A pants blaster is a fart so explosive it blows your pants off, leaving only the waistband.

Often encountered after a taco and beer binge.
Fred's friends heard a gigantic fart and then saw him staggering down the stairs covered in poop, wearing only the waistband of his jeans.

"Pants blaster," said Syd.

"Open a window," said Geoff.