Noun. An piece of high quality weapons-grade explosive bant that one drops on or plants in a conversation.
Noun. Colloquial. A nugget of chat so stinky that when it is dropped (usually by a bantex or chob) any bonhomie in the surrounding area is instantly blown away. If the banter bomb is particularly explosive only a banter machine will be able to prevent any joie de vivre being sucked ruthlessly away from those unfortunate enough to be in the vicinity.
Origin: Men going on tours together and becoming morally reprehensible
'It was all going well in there until the Chob piped up and dropped that banter bomb about his girlfriend not looking like a clown'