ADAMANT

adamant, adamantine, inexorable, intransigent

(adjective) impervious to pleas, persuasion, requests, reason; “he is adamant in his refusal to change his mind”; “Cynthia was inexorable; she would have none of him”- W.Churchill; “an intransigent conservative opposed to every liberal tendency”

diamond, adamant

(noun) very hard native crystalline carbon valued as a gem

Source: WordNet® 3.1

Etymology

Adjective

adamant (comparative more adamant, superlative most adamant)

(said of people and their conviction) Firm; unshakeable; unyielding; determined.

(of an object) Very difficult to break, pierce, or cut.

Synonyms

• See also obstinate

Noun

adamant (plural adamants)

An imaginary rock or mineral of impenetrable hardness; a name given to the diamond and other substances of extreme hardness.

An embodiment of impregnable hardness.

(obsolete) A lodestone.

Source: Wiktionary

Ad"a*mant, n. Etym: [OE. adamaunt, adamant, diamond, magnet, OF. adamant, L. adamas, adamantis, the hardest metal, fr. Gr. adamare to love, be attached to, the word meant also magnet, as in OF. and LL. See Diamond, Tame.]

1. A stone imagined by some to be of impenetrable hardness; a name given to the diamond and other substance of extreme hardness; but in modern minerology it has no technical signification. It is now a rhetorical or poetical name for the embodiment of impenetrable hardness. Opposed the rocky orb Of tenfold adamant, his ample shield. Milton.

2. Lodestone; magnet. [Obs.] "A great adamant of acquaintance." Bacon. As true to thee as steel to adamant. Greene.

Source: Webster’s Unabridged Dictionary 1913 Edition