Acronym for the phrase "king turd." A king turd is the the largest (or very close) shit you've ever taken; a log so big it fills the bowl, peeks out of the water, and makes you proud to have fathered something so awe inspiring. It is illegal to not take a picture and show it to all your friends.
"Dude, I just ate a load of meat and potatoes. I'm gonna have a KT later with pics to prove it."
"Someone left an epic KT in the stall. I swear it was this big."