Huck - drop with 0 style.
girly out - easy side of the trail bypassing the scary section
rail - take a corner perfectly at full speed with no loos and sometimes and increase in speed
skinny - narrow bridge usually 6in a narrower that overpasses, well, anything we feel like
fatty - ... Guess

...
BTW I am a mountain biker...my slangs don't usually apply to roadies