Phrase used by two close people for one to describe that the other has been acting up the sneaky and the slimy attitude. Particularly common use is after a non broken non significant promise; like not to tickle the other during a hug after a whole bunch of tickling prior to it has occurred.
Me: trust me I wont tickle you, its a trust exercise!
Jake: okay
Me: *hugs but then starts tickling furiously*
Jake: YOU'RE A SKEEZ