To have your asshole or vagina gaped open by a giant cock or cock shaped device. To have it suspended open when something is pulled out, to gape or be gaping.
Bob took his huge girthing cock and gaped her ass. You could see through time!
To stretch the asshole of some unfortunate to such an extent by fucking it that it "gapes" open after retraction. To make someone your bitch by fucking them over.
Man, I got fucking gaped at the football tonight, we got pumped. My asshole looks like a fucking blunderbus.