According to BBC, "mechanical motion" is defined as one of the four different motion types in mechanical systems. They are rotary motion, linear motion, reciprocating motion and oscillating motion.
Rotary motion is turning in circles like a wheel, and linear motion is motion in a straight line like a paper trimmer. Reciprocating motion is a backwards-and-forwards motion like a saw in a straight line, and oscillating motion is a swinging from side-to-side motion, such as a clock's pendulum. Mechanical systems often have one type of input motion and a different type of output motion. An example of this type of mechanism is a chain and sprocket, which changes a rotary motion to a linear motion.