The opposite of fun.
My date last night was horrible! No matter what I suggested, she just didn't want to do anything! She was so antifun!
ayon kay Babo Sang Pyo ika-30 ng Oktubre, 2005
1 more definition
Someone who is absolutely hell-bent on not having a good time or, more importantly, has a great way of curtailing others having a fun time
My boss wouldn't let me have an hour off to catch the game. He really is the anti fun
ayon kay Neil73 ika-26 ng Marso, 2007