To masturbate furiously. So hard, in fact, that it makes a wet "fap" noise repeatedly. the double "p" in this word is because it is the abbreviated version of "Fapping".
John: eww! what are you doing!!?
Jake: (fapfapfapfapfap) hey man! everybody fapps!
John: let go of my cat!
A mobile phone application that is so good it makes you want to thrash your man baton repeatedly.
'Hey, what's that app like?'
'It's awesome! It's not just an app, it's a fapp!'