The onomatopoeic representation of masturbation. Often used to suggest that something is attractive.

A sound effect for masturbation used often in japanese comics. Popularized in the english speaking world by the webcomic www.sexylosers.com

The sound made when you jack off.

The onomatopoeic representation of male masturbation.
Often used to suggest that something is attractive.
It can also be used to suggest that something is cute, or that something tastes good, or simply that the person using the word greatly approves of whatever he/she (mostly he) says 'fap' to.

To milk the tube steak for all it's worth.

To masturbate, to jerk off

To play with oneself (for females, this is shikking oneself)