The term DECREASE THE VELOCITY OF can be solved by two crossword solutions: IRON (4 letters) and LESSEN (6 letters). IRON is a chemical element that is found in nature and is used to make steel, which is a strong and durable material. LESSEN is a verb meaning to reduce or make something smaller in size, amount, or degree. Therefore, the two crossword solutions for DECREASE THE VELOCITY OF are related to reducing the speed of something.