The act of using your thumb to plug any orifice of the human body. Whether in a life or death situation, or in a sexual context.
Example 1: Dang dude, if it wasn't for Scott's thumb, he'd be dead.
Yea man, that Kentucky Plug was a life saver.
Example 2: Hey girl, you wanna get that Kentucky Plug tonight?
Using your thumb (primarily someone from Kentucky) to plug any holes on the human body whether in sexual or non-sexual context.
Brandon: Hey Scott, I gave my wife the good ol' Kentucky thumb after your "incident"
Scott: That's great man, I'm happy to hear that.