The crossword solution for the term 'REVERSE, SAY' is GEAR, which is a four-letter word. GEAR is a mechanical device consisting of a toothed wheel or cogwheel that meshes with another toothed part in order to transmit torque. Gears are used to change the speed or direction of a rotating shaft, such as in a motor or engine. In this context, the term 'REVERSE, SAY' is referring to the fact that gears can be used to reverse the direction of a rotating shaft.