when a man cant get his thoughts out of the gutter and verbally exercises his manhood toward a female with grunts and whistles or pelvic thrusts to mid air.. ,or just simply being an insensitive prick with man brain stupidity .For he may be excused by announcing (my apologies I'm having a Man Brain Moment) or in text ..(sorry luv im having an MBM..)

When a nigga says some smart shit and the brain begins to get fucking large and niggas can see that shit. They notice and call you a nigga having a big brain moment.

When you forget something incredibly important in a matter of seconds.

If you're a (big brainer) then you've most likely experienced a so-called "Big Brain Moment". But to all you low-class MacDonnals workers, a big brain moment is when you get such a good idea, that you just have to yell it, so everyone can hear how clever you are.

When one speaks a thought and immediately regrets it, wishing their mouth had stayed firmly closed whilst being mercilessly mocked.