Word of the Day:

1 : made of or having the quality of adamant

2 : rigidly firm : unyielding

3 : resembling the diamond in hardness or luster

The ushers were adamantine in their refusal to let latecomers into the theater.

"Lampard and Pirlo have been adamantine, but even Lampard fell prey to injury this past season." — Rafael Noboa y Rivera, Hudson River Blue, 17 June 2015

More example sentences

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 used in similar contexts. The English noun adamant (meaning "an unbreakable or extremely hard substance"), as well as the adjective adamant (meaning "inflexible" or "unyielding"), came from adamas. Adamantine, which also has such figurative uses as "rigid," "firm," and "unyielding," came from adamantinus. Adamas is actually the source of diamond as well. Diamas, the Latin term for diamond, was an alteration of adamas.