Webster’s New World College Dictionary, Fourth Edition, compiled by the
editors of Webster’s New World Dictionaries. Copyright © 2010 by Houghton
Mifflin Harcourt. Published by Houghton Mifflin Harcourt. All rights reserved.
Word origin of 'inexpugnable'LME < MFr < L inexpugnabilis < in-, not + expugnabilis, that can be taken by storm < expugnare, to take by storm < ex-, intens. + pugnare, to fight: see pugnacious