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1.
1. To desire something greatly; to need badly.

2. To be moving at outrageous speeds
1."Hey Bob, come out for a smoke?" "Hell yeah, I'm fanging, dude".

2."So we were fangin' down the freeway when Jimmy dropped the bong in the backseat."
by RealBadMike November 19, 2007
 
2.
An abbreviation for the the American slang "Finger-Bang'. While typically used as a verb it may be used as a adjective with only slight modification.
verb: 'I was fanging the shit out of that girl on Rock-Rimmon the other night.'

adj: "That skank sho' is fang-tastic!" or 'Her shit was "Fanger-lickin-good!"
by Friend of Fang May 27, 2010
 
3.
Euphemism in Werewolf parlance for devouring livestock with bloodlusting abandon.
After 300+ years, touching six continents, and fanging scores of sheep, I've learned the only bad cocktail is a finished cocktail.
by Wolfman Bartender November 04, 2011