Acronym for a group called Men's Rights Activists.
I.E. - A bunch of whiny pedantic morons that think there is some vast Illuminati feminist conspiracy while seemingly ignoring the fact that their own gender runs the majority of the world.
- Hey, you hear about that guy in Marketing that complains about his ex-wife all the time?
-- Yeah, I heard that he just got a raise and tried to take his ex to court to reduce his child support.
- Jeez, what a MRA.