the sensation one experiences--ie, on a roller coaster, or a very high swing as a child, or driving fast down a steep hill, or falling in a dream--that causes your body to suddenly tense and your anus to pucker inward reflexively and with force, as if your ass is 'biting down' as a result of the sensation; an autonomic ass pucker
Parasailing makes my ass bite.
Suck-Shit (noun) - some action or person that's really dreadfully crappy; something worse than the worst.
This day totally sucked. I'm just grateful this suck-shit is over.
OMG, don't cry over him! He treated you like total suck-shit!
