Servo-motor
Pronunciation : Ser`vo-mo"tor
Part of Speech : n.
Definition : Defn: A relay apparatus; specif.: (a) 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. (b) In a Whitehead torpedo, a compressed-air motor, for moving the rudders so as to correct deviations from the course.
[Sometimes erroneously spelt serro-motor.] [F. servo-moteur. See Serf; Motor.] (Mach.)
Source : Webster's Unabridged Dictionary, 1913