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..)
out on the town with the misses she accidentally drops the keys and bends over in front of you,you grab her but and start pretending pelvic thrusting with one arm in the air swayin..thats havin a man brain moment .or shes balling her eyes out and you say whats the footy score!! oops sorry luv 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.
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.
Me a highly intellectual: Hey (Brad)
Brad: Ya bra
Me: You know what I just got?
Brad: Nah brah
Me: I just had this really good idea, but I ain't gonna tell you it, because, you're not clever enough to understand my superior brain (Laughs in a high IQ voice), boy oh boy I do like when I get these Big Brain Moments.
A phrase used to convey a moment, when someone does something out of either habit or instinct. Not to be used as a joke in front of an actual brain dead person.