The term 'Lunar Trench' refers to a type of feature found on the surface of the Moon. It is a long, narrow depression that is usually several kilometers in length and can be up to several hundred meters deep. The two crossword solutions for this term are 'RILL' and 'Rille'. A RILL is a shallow channel or groove that is typically formed by running water, while a rille is a larger, deeper trench-like feature that is usually formed by volcanic activity.