The crossword solution for the term 'TURN TO VINEGAR' is 'ACIDIFY'. This term refers to the process of turning a liquid into vinegar, which is an acidic liquid. Vinegar is made by fermenting ethanol, which is a type of alcohol, and is used in many culinary dishes and as a cleaning agent. The process of acidifying a liquid involves adding an acid, such as acetic acid, to the liquid in order to lower its pH level.