Gangsta term used in place of a comma, period, question mark, or any other form of punctuation. Derived from "Do you know what I am saying?".
Also used to denote occasions when the speaker is completely full of shit.
Well Maury num-sain I am ten thousand percent sure num-sain dat Quontery's triflin' and scan-lus ass num-sain be my Baby Daddy num-sain!
Furthermore num-sain I have no concept of how percentages work num-sain!