crankin' dat

when a person, usually male, masturbates

Lisa: "Hey, did you guys see where Danny went? I haven't seen him for like fifteen minutes."

John: "Last time I saw him, he was in the locker room, crankin' dat Danny with a playboy"

Crankin dat soulja boy

Although widely known as a dance from 2007 created by Soulja Boy Tellem, the phrase also refers to male masturbation. The reason it is known as such is because the penis is similar to a solider with its helmet, and it is cranked like a crankshaft during masturbation.

"I walked in on dat nigga, and he was Crankin dat soulja boy, so I dipped."