• synonyms


[yoo-ni-len-ee-uh m]
noun Chemistry, Physics.
  1. former name of meitnerium. Symbol: Une
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Also called element 109.


[mahyt-nur-ee-uh m]
noun Chemistry, Physics.
  1. a superheavy, synthetic, radioactive element. Symbol: Mt; atomic number: 109.
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Origin of meitnerium

named after Austrian physicist Lise Meitner;see -ium
Formerly unnilennium, element 109.

element 109

noun Chemistry, Physics.
  1. meitnerium.
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Formerly unnilennium.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for unnilennium


  1. a synthetic element produced in small quantities by high-energy ion bombardment. Symbol: Mt; atomic no: 109
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Word Origin for meitnerium

C20: named after Lise Meitner
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

unnilennium in Science


  1. A synthetic, radioactive element that is produced by bombarding bismuth with iron ions. Its most long-lived isotopes have mass numbers of 266 and 268 with half-lives of 3.4 milliseconds and 70 milliseconds, respectively. Atomic number 109. See Periodic Table.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.