Also found in: Thesaurus, Medical, Encyclopedia.
n. pl. tri·so·mies
The condition of having three copies of a given chromosome in each somatic cell rather than the normal number of two.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
(Biology) a chromosome occurring three times (rather than twice) in a cell
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014