mettle
noun

- the ability and determination to do something successfully despite difficult conditions

Oxford Learner's Dictionary

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ORIGIN

mid 16th century: specialized spelling (used for figurative senses) of metal.

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SYNONYMS

spirit, calibre, fortitude, tenacity, character, strength of character, moral fibre, steel, determination, resolve, resolution, steadfastness, indomitability, backbone, hardihood, pluck, nerve, gameness, courage, courageousness, bravery, gallantry, valour, intrepidity, fearlessness, boldness, daring, audacity; IDIOMS: Dunkirk spirit; guts, grit, spunk, bottle

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Find an opportunity to SMUGGLE OWAD into a conversation:

"The next negotiating round will be a real test of their METTLE."