[ mod-uh-rey-ter ]
See synonyms for moderator on
  1. a person or thing that moderates.

  2. a person who presides over a panel discussion on radio or television.

  1. 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.

  2. a presiding officer, as at a public forum, a legislative body, or an ecclesiastical body in the Presbyterian Church.

  3. Physics. a substance, as graphite or heavy water, used to slow neutrons to speeds at which they are more efficient in causing fission.

Origin of moderator

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

Other words from moderator

  • mod·er·a·to·ri·al [mod-er-uh-tawr-ee-uhl, -tohr-], /ˌmɒd ər əˈtɔr i əl, -ˈtoʊr-/, adjective
  • mod·er·a·tor·ship, noun

Words Nearby moderator Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use moderator in a sentence

British Dictionary definitions for moderator


/ (ˈmɒdəˌreɪtə) /

  1. a person or thing that moderates

  2. Presbyterian Church a minister appointed to preside over a Church court, synod, or general assembly

  1. a presiding officer at a public or legislative assembly

  2. a material, such as heavy water or graphite, used for slowing down neutrons in the cores of nuclear reactors so that they have more chance of inducing nuclear fission

  3. an examiner at Oxford or Cambridge Universities in first public examinations

  4. (in Britain and New Zealand) one who is responsible for consistency of standards in the grading of some educational assessments

  5. a person who monitors the conversations in an on-line chatroom for bad language, inappropriate content, etc

Derived forms of moderator

  • moderatorship, 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

Scientific definitions for moderator


[ mŏdə-rā′tər ]

  1. 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.