A term used when some is trying to get with someone else.
Jose: Dude, why is Leah always jumpin' my jock?
John: She's just desperate. You're like the fourth guy this month.
Mike: Why does Kelsie jump Steve's jock every time he's around?
Josh: Dude, you know she's liked him since Freshman year. Give her some slack.
Jake: Hey Kristi, why do you gotta jump jock so much? This is like your fourth boyfriend this month!
Kristi: It's not my fault there are so many cute guys!
Jake: But all your boyfriends are ugly...