Adamantine

 WORD OF THE DAY

adamantine / adjective / ad-uh-MAN-teen

Definitions

1: made of or having the quality of adamant
2a: rigidly firm
2b: unyielding
3: resembling the diamond in hardness or luster

Examples
"The black-and-white illustrations … conjure up wind-borne snows, cliffs that rear up like waves, and waves that look as adamantine as rock."
— Susannah Clapp, The Observer (London), 5 June 2021

Davosites are defined by their adamantine belief in economic and social liberalism and their position at the top of various global organisations.
— The Economist, 16 Nov. 2019

Did You Know?
The Greek and Latin word for the hardest imaginable substance, whether applied to a legendary stone or an actual substance, such as diamond, was adamas.
Latin poets used the term figuratively for things lasting, firm, or unbending, and the adjective adamantinus was applied in similar contexts.
The English noun adamant (meaning "an unbreakable or extremely hard substance") as well as the adjective adamant ("inflexible" or "unyielding") came from adamas.
Adamantine, however—which has such figurative uses as "rigid," "firm," and "unyielding"—came from adamantinus.
Adamas is also the source of diamond. Diamas, the Latin term for diamond, is an alteration of adamas.