cab means switch backside (i think, maybe it's fs), but since skiers don't have bs and fs it's kind of meaningless. people just use it as another word for switch.
Cab comes from skateboarding's steve cabelerro who fakie backside 360ed. it was later applied to snowboarding to mean any switch spin and then to skiing, so it doesnt have anything to do with cork, or bio, or unnatty, just switch spins. Props to whoever did that cab five.