A sound that one says when one is overly excited or pumped up. A term of agreement (common among pirates). A combination of the words yar and byah(from The Chappelle Show).
Chris: Yo did you see Kobe drop 40 on the Suns last night?
Hannah: Chris do you wanna hang out tonight?
Chris: Are you going to show me your titties?
Chris: BYAR! Man I am so pumped we won that game.
Bob: Byar man me too!