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[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.
1350-1400; Middle English < Latin moderātor, equivalent to moderā() to control (see moderate) + -tor -tor
Related forms
[mod-er-uh-tawr-ee-uh l, -tohr-] /ˌmɒd ər əˈtɔr i əl, -ˈtoʊr-/ (Show IPA),
moderatorship, noun Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for moderator
  • My posting on this forum was deleted by the moderator.
  • Graphite is a great moderator, slowing down the neutrons and keeping their reaction in the proper temperature range.
  • The entire staff is trying to write a mission statement with help from a moderator.
  • Also, the moderator's questions to both candidates are going to be the same, it shouldn't matter.
  • The resultant salt mixture simultaneously works as a moderator, coolant, and fuel medium.
  • Once your first comment is posted by a moderator, all future comments will post automatically.
  • The nearby ocean water acts as a temperature moderator, since water takes longer to both heat and cool than land.
  • Let's see if this neutral comment survives the immoderate moderator's ministrations.
  • And you are encouraged to air your own views by sending comments to the moderator.
  • Since water is a moderator, it cannot be used as a coolant in a fast reactor.
British Dictionary definitions for moderator


a person or thing that moderates
(Presbyterian Church) a minister appointed to preside over a Church court, synod, or general assembly
a presiding officer at a public or legislative assembly
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
an examiner at Oxford or Cambridge Universities in first public examinations
(in Britain and New Zealand) one who is responsible for consistency of standards in the grading of some educational assessments
a person who monitors the conversations in an on-line chatroom for bad language, inappropriate content, etc
Derived Forms
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
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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
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moderator in Science
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 © 2002. Published by Houghton Mifflin. All rights reserved.
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moderator in Technology

A person, or small group of people, who manages a moderated mailing list or Usenet newsgroup. Moderators are responsible for determining which email submissions are passed on to the list or newsgroup.

The Free On-line Dictionary of Computing, © Denis Howe 2010
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