The term METRIC SYSTEM UNIT can be summarized as a unit of measurement used in the metric system. The metric system is a decimalized system of measurement based on the meter, kilogram, and second. It is the most widely used system of measurement in the world and is used in science, industry, and everyday life. The crossword solution for this term is GRAM, which is a unit of mass in the metric system equal to one thousandth of a kilogram.