Used to describe the last day of the working week when members of an office bring in sweet sugary buns, doughnuts, cakes and pastries for everyone else to binge on. The Starbucks Cinnamon bun is a good Fun Bun Friday staple as is the Krispy Kreme dozen donut box.
Secretary 1: Sandy, what day is it today?
Secretary 2: It's Wednesday dude...
Secretary 1: Damn...still two days left until Fun Bun Friday!
Secretary 2: Don't remind me! In fact I feel like a fun bun right now...
Secretary 1: F**k it. Let's go to Starbies!
Secretary 2: Cool...let's roll!