When a serious injury happens and a thumb or other cylinder shaped body part is used to plug up the injury. Or referred to as a sex position, when a man puts a finger or penis in a woman’s butthole. And some people who use this sex position are referred to as “donut operators”
Sexual action involving the thumb in the womans Vagina with index and pointer spreading the Labia allowing the middle finger to articulate the citrous. the three fingers form a "K" (as in Kentucky) And thumb acts as a "plug"
I was watching my buddyscott's youtube and he said just "stick a thumb in it" sure enough I gave my GF the Kentucky Plug and had her in a euphoric daze