Composed of or resembling adamant; extremely hard, impenetrable, or unyielding.
From 'adamant' + '-ean' (adjective suffix creating quality of something). A rare variant of 'adamantine,' formed in classical English during the 17th-18th centuries.
Adamantean is what happens when suffix creativity goes wild—English speakers had 'adamantine' but still created 'adamantean,' showing how language constantly generates synonyms for emphasis, though only the shortest versions survive.
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