-atorsuff. One that acts in a specified manner: radiator.[Latin -?tor : -?-, stem vowel of verbs in -?re + -tor, agent n. suff. (later reanalyzed as -?tus, -ate + -or, -or).]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.-ator suffix forming nouns a person or thing that performs a certain action: agitator; escalator; radiator. [from Latin -?tor; see -ate1 -or1]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014-ator a suffix that forms nouns corresponding to verbs ending in -ate1, denoting a human agent (agitator; mediator) or nonhuman entity, esp. a machine (incubator; vibrator) performing the function named by the verb. Compare -tor, -or2. [