Green’s Dictionary of Slang

fap v.

[? echoic of the hand on flesh]

to masturbate.

motherless.com 20 Oct. 🌐 i confess i enjoy fapping to my cousin. what do you think of her?
[US]Salon.com 21 Oct. 🌐 The obvious reason why people cap these shows is so that they can watch it again to ‘Fap’ [masturbate] to later on or so that they can show their friends what they missed out [on].