the nutritious drink formed by the sweat between your anus and ballsack.
after taking his face out of ferman's ass, kenny quickly realized it was smeared with grundle sauce.
by beastiality December 06, 2005
the juices or sauce that forms between your asshole and nutsack. also known as duck butter
damian love his grundle sauce on his breakfast toast.
by kne December 02, 2005