A diluting agent is a substance that is added to another substance to reduce its concentration or strength. The most common example of a diluting agent is water, which is often used to reduce the strength of an alcoholic beverage. In this crossword, the solution for the term 'diluting agent' is 'THINNER', which is a type of diluting agent that is used to reduce the viscosity of a liquid. THINNER is typically composed of a mixture of solvents, such as mineral spirits, turpentine, and acetone.