Obvious Reason Boner. Opposite of NRB (No Reason Boner). When one has a boner, and there is an obvious reason present for said boner. I.E: Getting a lap dance at a strip club, holding hands with a girl for the first time, watching a sex scene in a movie or watching horse races.
Wade: "Uhhhhh h-h-hi Zooey Deschanel, n-n-n-nice to meet you!"
Zooey: "Nice to meet you too, Wade. By the way, nice ORB."