Messed Up Monday Share definition Flag Messed-Up-Monday is a slang term to describe getting drunk on Mondays. Similar to Thirsty Thursdays or Sober Sundays. Hey do you want to get drunk tonight?"Sure its Messed Up Mondays, lets get fucked up" Messed Up Monday by chroine November 9, 2009 0 0 Get merch Get the Messed Up Monday mug. Buy Now — $32.95 See more merch