The term 'Tub Stopper' refers to a device used to seal a bathtub drain. The two crossword solutions for this term are 'AVAST' (5 letters) and 'PLUG' (4 letters). AVAST is an interjection used to express surprise or alarm, while PLUG is a noun that refers to a device used to fill a hole or close an opening. Together, these two words describe the function of a Tub Stopper, which is to fill the drain hole in a bathtub and prevent water from escaping.