While in the midst of coitus with the female partner being taken from behind the male applies a liberal amount of lubrication to the entrance of the female's rectum. The male then proceeds to insert a string of anal beads into the rectum of his partner. As the man climaxes he concurrently removes the beads in one quick motion. In a manner similar to starting a chainsaw. The resulting effect is a noise resembling the starting of an oily chainsaw which sprays oil in the immediate vicinity.
Bro 1: "What was that noise last night from your room?"
Bro 2: "Oh, that was me giving Lilly an oily chainsaw. God the smell was terrible and now I have to repaint my wall."