Broken down version of "You know what I am saying?". Often used by a guy seeking agreeance from his homies after he has made a statement. Do not use if A.) The statement or idea is stupid or fucked up, in which case "nah sayn" may backfire terribly on you. B.) If you think no one will agree with you, again leading "nah sayn" to backfire on you. C.)If you are white and can not make a deep enough "G" voice when saying "Nah Sayn";That will often lead to someone saying "Man Shut Up." Synonyms: See Nah Mean and Ya Heard?
Michael: Man, Brandon's mom is a milf, I would tear that ass up..Nah Sayn?
Kyle, Anthony, Nathan, Sean, rest of corner at lunch: Yeah fo sho dawg, every position in the book.

Michael: Nah Sayn Playa?
Gabe S: Yea.
by Mike Op January 20, 2008