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undecagon

American  
[uhn-dek-uh-gon, -guhn] / ʌnˈdɛk əˌgɒn, -gən /

noun

  1. a polygon having 11 angles and 11 sides.

undecagon British  
/ ʌnˈdɛkəˌɡɒn /

noun

  1. a polygon having eleven sides

"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

Etymology

Origin of undecagon

1720–30; < Latin un-, as in undecim eleven ( ūn ( us ) one + -decim, combining form of decem ten ) + decagon

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.