adamantine

[ ad-uh-man-teen, -tin, -tahyn ]
/ ˌæd əˈmæn tin, -tɪn, -taɪn /

adjective

utterly unyielding or firm in attitude or opinion.
too hard to cut, break, or pierce.
like a diamond in luster.

Origin of adamantine

1200–1250; Middle English < Latin adamantinus < Greek adamántinos. See adamant, -ine1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for adamantine

British Dictionary definitions for adamantine

adamantine

/ (ˌædəˈmæntaɪn) /

adjective

very hard; unbreakable or unyielding
having the lustre of a diamond

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