A phrase generally used in Northern Ireland meaning "any news", or something to that effect. It's answered with "nothing much" even if you do have news.
"What's the crack?"
"Nothing much. Oh, I won the lottery!".
"Class!"
V: to use your hands to open each side of your gluteus maximus to expose the rectum, then sit on an object while making sure that the rectum touches the desired object.
Rodney butt cracked Chris's pillow to get him back for that prank he pulled earlier.