To be so incredibly surprised, confused, or astonished by an action, statement, or situation that no other word can describe what you have experienced or heard.
Dude I'm completely boofounded that you actually milked that cat.
To take something small, that doesn't quite qualify as a theft. Probably from the Danish "skæv" or the Dutch "scheef", both of which are pronounced similarly, meaning "askew, or not quite right'. To change an item's ownership without permission, but only something small and of little worth.
"I skeefed an apple off the neighbor's tree." "I skeefed some chips outta your bag when you looked away." "Don't skeef my chair when I go to the bathroom."