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1.
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.
by Dr. Bison January 19, 2011
 
2.
A day to skip class, sleep in and get drunk.... really really really drunk.
Bison Day, the REAL reason people go to college.
by CanIGetAHottub February 03, 2011