The crossword solution for the term LEAN BACKWARD is ARCH, which is a four-letter word. An ARCH is a curved structure that is used to span an opening and support the weight above it. Arches are commonly used in architecture and engineering, and they can be found in bridges, doorways, and other structures. Leaning backward is a motion that involves bending the spine backwards, usually in a relaxed manner. This motion can be used to stretch the back muscles and improve posture.