[ mod-uh-rey-ter ]
/ ˈmɒd əˌreɪ tər /


a person or thing that moderates.
a person who presides over a panel discussion on radio or television.
a member of an online message board or electronic mailing list with privileges and responsibilities to approve or reject messages and uphold the terms of service.
a presiding officer, as at a public forum, a legislative body, or an ecclesiastical body in the Presbyterian Church.
Physics. a substance, as graphite or heavy water, used to slow neutrons to speeds at which they are more efficient in causing fission.

Nearby words

  1. moderately,
  2. moderation,
  3. moderationist,
  4. moderations,
  5. moderato,
  6. modern,
  7. modern apprenticeship,
  8. modern art,
  9. modern cut,
  10. modern dance

Origin of moderator

1350–1400; Middle English < Latin moderātor, equivalent to moderā(rī) to control (see moderate) + -tor -tor

Related formsmod·er·a·to·ri·al [mod-er-uh-tawr-ee-uh l, -tohr-] /ˌmɒd ər əˈtɔr i əl, -ˈtoʊr-/, adjectivemod·er·a·tor·ship, noun Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for moderator

British Dictionary definitions for moderator


/ (ˈmɒdəˌreɪtə) /


Derived Formsmoderatorship, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for moderator



late 14c., "ruler, governor," from Latin moderator "manager, ruler, director," literally "he who moderates," from moderatus (see moderate (adj.)). Meaning "one who acts as an umpire" is from 1560s. Fem. form moderatrix attested from 1530s.

Online Etymology Dictionary, © 2010 Douglas Harper

Science definitions for moderator


[ mŏdə-rā′tər ]

A substance, such as graphite, water, or heavy water, placed in a nuclear reactor to slow neutrons down to speeds at which they are more likely to be captured by fissionable components of a fuel (such as uranium-235) and less likely to be absorbed by nonfissionable components of a fuel (such as uranium-238). Also called neutron moderator See also slow neutron.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.