A man who has fast but not deep penetration during sex, similar to a jack rabbit popping his head in and out of a hole quickly. Usually only a little more than the tip of the penis enters, and it is quickly removed repeatedly so as to only stimulate the head of the penis.
It can be used as a verb and a noun
Girl 1: "How was your date last night? I heard that guy jack rabbits."
Girl 2: "Yeah, he's a Jack rabbit all right. Speedy dick barely got in there."
Girl 1: "What's with guys jack rabitting all the time? It's so selfish."
Girl 2: "I don't know, maybe they think the faster the better? Anyway, I definitely won't fuck him again."