A maneuver in which a girl inserts a statement about her boyfriend to let any would-be suitors that she is already taken. In some cases it is used by single women who want to let a guy know that she isn't interested. Despite the violent name of this act, also called the boyfriend drop, and the pain it may cause for the male recipient, the boyfriend bomb is actually an act of kindness in either case. The girl is simply trying to show that she is taken or not interested, before the guy asks her out and makes an ass of himself.
As soon as I could tell he wasn't just being friendly, I hinted to him that I had a boyfriend so that he wouldn't get his hopes up.
That guy at the bar seemed really nice, he just wasn't my type, so I lied and dropped the boyfriend bomb as to not hurt his feelings.