A term used in telling someone who is already mad to get madder. This implies that you're encouraging the angry person to submit to their rage, basically telling them to give up. If the angry person was truly determined about what they were doing or about the situation they won't get mad.
Guy 1 - "Man, I can't get this fucking car to start, DAMN!!"
Guy 2 - "What, you mad? Get mad dude"
Guy 1 - "nah, I got this" (<--implies only to people who r man enough to not get mad)