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[tuh-mok-suh-fuh n, ‐fen]
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noun Pharmacology.
  1. an antineoplastic drug, C26H29NO, that blocks the estrogen receptors on cancer cells, used in the treatment of breast cancer.

Origin of tamoxifen

1970–75; perhaps t(rans)- + am(ino)- + oxy-2 + phen(yl), with respelling of y and ph
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for tamoxifen


  1. a drug that antagonizes the action of oestrogen and is used to treat breast cancer and some types of infertility in women

Word Origin

C20: altered from t (rans-) + am (ine) + oxy- ² + phen (ol)
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

tamoxifen in Science


  1. An estrogen antagonist drug used to treat advanced breast cancer in women whose tumors are estrogen-dependent and to prevent breast cancer in some women who are at high risk.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.