What is "servo-motor"

Servo-motor \Ser`vo-mo"tor\ (s[~e]r`v[-o]*m[=o]"t[~e]r), n. [Sometimes erroneously spelt serro-motor.] [F. servo-moteur. See Serf; Motor.]

1. (Mach.) A relay apparatus; specif.:

   1. 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.

   2. In a Whitehead torpedo, a compressed-air motor, for moving the rudders so as to correct deviations from the course.

2. a motor which forms part of a servomechanism.