A secret phrase between two men at a social gathering or sporting event where they can alert the other that a chick with nice breasts is in the vicinity without alerting those around them. The term is simply boob minus an o. Boob-o=bob.
1st Dude: "Hey look there's Bob!" (Points at breast)
2nd Dude: "I am so glad he could make it. I was worried he wouldn't."