The crossword solution for the term PROOF MEASURES IT is ALCOHOL. ALCOHOL is a type of chemical compound that is made up of carbon, hydrogen, and oxygen atoms. It is commonly found in alcoholic beverages such as beer, wine, and spirits. ALCOHOL has been used for centuries as a way to measure the strength of a beverage, with the term 'PROOF' referring to the amount of ALCOHOL present in a drink. The higher the PROOF, the more ALCOHOL is present.