a combination of -ate 1 and -or 2 that forms nouns corresponding to verbs ending in -ate 1,denoting a human agent (agitator; mediator; adjudicator) or nonhuman entity, esp. a machine (incubator; regulator; vibrator) performing the function named by the verb. Cf. -tor, -or2.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.