Acronym for "NOM SANE BRUH" which is the short way of saying "Do you know what I am saying, brother?"
Alternatively, it can be the reciprocal "NAWR SANE BRUH" which is the short way of saying "I do know what you are saying, brother!"
A:Yo man she's so hot... but in a cute way, nsb?
B:Yeh. I nsb.
A:This track is tripping me out, but I ain't high, nsb?
B:YE I NAWR SANE BRUH NSB NSB NSB