Stands for: Men-Are-Bastards

A mindset in which a female or male temporarily or permantely believes that all members of the male gender are bastards, often due to a viscious break-up or negative relationship.
Jen was cheated on so now she's in a MRB mindset.
by CheeseCookies September 11, 2009
Acronym for "mad random boner" -archaic, inf. Circa early 2000s
Greg would have been on time for his next class, but he got an MRB at the end Home econ, and had to stay seated for a few minutes to conceal it while it went down
by Dang8701 September 28, 2021
Mega Raging Boner, referring to yourself
Well i have a MRG baby!
by Manny Fresh June 27, 2005