An individual who is undeniably bro, but not everday. The rest of the time, he may as well be pmsing.
Are you gonna hang out with Justin today?

No idea. That fucker is so bropolar, I never can tell with him.
by albinobro October 12, 2011
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When you're a good human but tend to revert back to your bro, fuckboy tendencies.
Trevor's not a bad guy, he's just bropolar.
by Torque Thunder December 29, 2016
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