moderator definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a person or thing that moderates; specif.,
- a person who presides at a town meeting, debate, assembly, etc.
- the presiding officer of a governing body, as of the Presbyterian Church
- a substance, as graphite or heavy water, used to slow down high-energy neutrons in a nuclear reactor
Origin: Middle English moderatour ; from Classical Latin moderator
moderator definition by American Heritage Dictionary
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
- One that moderates, as:a. One that arbitrates or mediates.b. One who presides over a meeting, forum, or debate.
- The officer who presides over a synod or general assembly of the Presbyterian Church.
- Physics A substance, such as water or graphite, that is used in a nuclear reactor to decrease the speed of fast neutrons and increase the likelihood of fission.
moderator - Science Definition
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.