Mouthwash instruction is a term used to describe the instructions given on the label of a mouthwash bottle. It typically includes directions on how to use the product, such as how long to RINSE and how often to use it. The crossword solution for this term is 'RINSE', which is an action that is usually part of the instructions. Rinsing with mouthwash helps to reduce bacteria in the mouth and freshen breath.