when you throw yourself under the bus to help a brother out. Usually when this psycotic whore stalks your bro and his gf/her "best" friend. usually she is a kind of cockblocker, and you are your bro's savior, like a Jeezus.
When Jack asked Bill to take that cockblocker Elizabeth's attention from Jack and Jill, Bill knew how much of a bromageddon this would turn out to be, so he said yes.
If you or someone you know had to sacrifice themself for a bitch so someone else could move in closer with their girlfriend, you have seen a bromageddon