Breastphyxiation

The act of suffocating someone with a large pair of breasts, usually a D cup or larger. This usually occurs when someone tries to motorboat a girl and it goes horribly wrong, causing him to asphyxiate within the girl's breasts.

John: Bro, did you hear about Dave?

Nick: No, what happened?

John: He was trying to motorboat some hot chick with a huge rack, but got lost in there and died.

Nick: Dude... *shakes head*

John: Yeah, the coroner said cause of death was accidental breastphyxiation.