Definition of "yass"

yass¹

particle
1. (US, dialectal, Scotland) Pronunciation spelling of yes.
  Quotations
  Yass. I never got above the rank of shavetail. We were the dogfaces who gave ’em hell at Chateau Thierry.
  1962, Joseph Commings, “The X Street Murders”, in The Mammoth Book of Perfect Crimes & Impossible Mysteries, published 2006

yass²

/jɑːs/

interjection
1. (African-American Vernacular, LGBT, slang) A strong expression of excitement or admiration.