The phrasal verb 'wash down' also means to clean the surface of something, using water, from top to bottom. Example: He washes the wall down every year before Christmas. Example: She washed the car down and then dried it. 'Wash off' also refers to the act of washing the surface of something with water. The purpose is to remove dirt or other unwanted substances. Example: She felt itchy after the mask had been washed off. Example: He tried to wash off the ink on his coat. If someone says he is washed out, he is very tired and has no energy. He hasn't had a bath!