shank the cat

To mess up the sistuation, to screw over a person or group of people by narking on them or mentioning someing to the wrong person. to tell a secret or reveal senstave information to people that could use it for blackmail.

see also shanked the cat

"Damn Tommy, you really shanked the cat this time, why did you tell melinda that i was allergic to her perfume!"

"Don't shank the cat billy, don't mention that you are involved with sally, OK!