look up any word, like pussy:
 
1.
to masturbate
jack off
normally used for a guy
but girls can also use it
"i was busy last night"
" you were fappin!"

"brb"
"you were fappin"

naughty talk
fappin!
by arielj November 11, 2007
 
2.
Fappin': Equivalent to words such as "smashing", "amazing" and the like.

Also means to yank ones penis ever so sensually.
Bubba: That's a FAPPIN' new pair of shoes you got there!
Jonathan: Why thank ye! I love fappin' while wearing these fappin' shoes!
by Pammy Pop April 16, 2014