When a female gender poops or sharts while wearing a thong. After this a male gender takes the soiled garment and holds it horizontally in front of a mirror. He then draws it back like a crossbow and snaps the shitty garment at the mirror, resulting in a fury of fecal matter on your mirror.
"Oh man I missed a spot shaving this morning because my roomate did a kentucky crossbow last night, and the mirror was filthy."
"The only good thing about that mexican restaurant was that my ol' lady got the shits, so I was able to do a few kentcuky crossbows last night