add. ·noun a relay apparatus;.
2. servo-motor ·add. ·noun in a whitehead torpedo, a compressed-air motor, for moving the rudders so as to correct deviations from the course.
3. servo-motor ·add. ·noun an auxiliary motor, regulated by a hand lever, for quickly and easily moving the reversing gear of a large marine engine into any desired position indicated by that of the hand lever, which controls the valve of the motor.