Bison day Share definition Flag A term used by NDSU students to describe a day of skipping classes and ignoring homework. Person 1: Hey bro, how's your week been?Person 2: Terrible. I'm thinking of taking a Bison day. Bison day by Dr. Bison January 20, 2011 0 0 Get merch Get the Bison day mug. Buy Now — $32.95 See more merch