A threshold of extreme anger, which results in a violent outburst if reached. The term is in reference to the classic Japanese role playing game "Lufia II: Rise of the Sinistrals", originally released on the Super Nintendo. In the game, each character acquires IP points whenever they are injured; the points can then be used to unleash special attacks on unsuspecting foes. Many players will refrain from using their special IP attacks until they have reached "Max IP", which is supposedly the breaking point of their characters' rage.
Man 1 - "What's with all the broken furniture?"
Man 2 - "Ah, it's my girlfriend... she found out I cheated on her with the ladies' badminton coach, and she just went totally Max IP."
Man 1 - "Damn... what the hell is Max IP?"