[MarkHenry]

Since you asked a question without any sarcasm attatched I feel it would be kind to answer your question truthfully. Please don't take offence in what "Fap" means, don't kill the messenger.
"Fap" is a modern slang used to say "Masturbate". Again, don't kill the mesenger. You asked, I answered.

Of course what was the contest in which the word fell? It may have been an acronym, but if it was like:
"I fap for Sarah Palin",
It obviousely ment something not "nice".
Don't kill the messenger.
You asked, I gave you an answer. Once again, can you explicitly say what the context was in which the word was used?