Not Tub Share definition Flag A would-be hot tub wherein the water is insufficiently heated to achieve the desired relaxant effect on the users. My boyfriend and I froze our asses off in the not tub. The hotel must be too cheap to heat it! Not Tub by wrightcountygirl August 30, 2010 0 0 Get merch Get the Not Tub mug. Buy Now — $32.95 See more merch