a motor and speed reducer combination where the two units are flanged for connection to each other and have one output shaft; or where the two units are closely coupled with the motor resting on a base which is an integral party of the speed reducing housing.

a motor with a gear head used for controlling the motor speed

An arrangement of an electric motor and a gearbox in one housing or connected by means of a "C" face mounting or other coupling method to form a single unit.