[ 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.

Origin of moderator

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


mod·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 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

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.