Whilst manipulating the scrotum with your mouth, shake your head back and forth making a "motorboat" engine sound.
It's the male version of the motorboat.

A polite term for shoving a lubricated probe into the Earth's hole to release gas.

v. int. The act of pushing one's face in between ones scrotum, and rocking one's head side to side very rapidly while making a vigorous, lip-vibrating "brrr" sound.

(Verb) the act of having the scrotum gargled while receiving oral sex.