servo, n. (pl. -os)
1 (in full servo-mechanism) a powered mechanism producing motion or forces at a higher level of energy than the input level, e.g. in the brakes and steering of large motor vehicles, esp. where feedback is employed to make the control automatic.
2 (in full servo-motor) the motive element in a servo-mechanism.
3 (in comb.) of or involving a servo-mechanism (servo-assisted).
L servus slave