Brain Bang is used to describe how you feel after witnessing something mind blowing or seeing something amazing and out of this world. It can also be used to describe how you feel after realizing somethingcrazy, like an epiphany on steroids.
Josh was brain banged when he realized that there was an arrow in the Fed Ex Logo and that OK is a stick figure side ways.
How did he pull that bunny out of that hat!? Man, what a Brain Bang.
Whoa! Inception gave me a crazy brain bang the whole time I was watching.
When a stripper at the club pulls a female customer on stage and begins to stick her fingers in or around the customer's pussy. This is likely done with the customer's nipples hanging out.
P1: Oh shit, look at those two strippers going at it!
P2: Those aren't two strippers, that stripper pulled that woman on stage.
P1: No shit, she just popped that civilian's titties out, now she is fingering her!
P2: Ah fuck! It's a civilian finger bang!