To grab a fleshy part on another's body, particularly on the underside of the upper arm, squeeze tightly, and then pull your fingers loose without loosening one's grip. Creates a bruise identical in appearance to the one produced by the bite of a horse.
Mr. Jones sent Bill to the office for giving other kids horsebites, noting that such severe bruising could cause blood clots.
pinkiejack horsepie is when a man buys a stuffed pinkie pie doll, and proceeds to tear a hole in the back to fuck it. After he cums in it he'll watch bojack horseman while sewing the doll back up.