Describes an appearance of an object not aligned the way one would expect it to be. This is not necessarily pejorative since an object could be designed or placed to be out of alignment.
"If you really want to put a king-size bed in that small room of yours, you will have to put it all tilty-wack just to get in and out of the room."
"That tabletop is tilty-wack. Everything rolls right off."