a Jkat, is a prison/jail term for a mentally unstable inmate, especially one that doesn't realize he is a weirdo. Derives from an inmate being a "Category J."
Meaning Just kidding all the way or jk all the way. Instead of the typical jk it refers to a past phrase as jkatw refers to the ENTIRE conversation..
Dave: Butter...Butter...Butter..
Jack: Dude whats wrong.
Dave: Ever drowned in butter
Jack: ......
Dave: No...well it involves lots of pushing, and a lot of shoving
Jack: Dude what are u talking about
Dave: haha jkatw
Jack: Idiot