last word, the

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The final statement in a verbal argument, as in Karen is never satisfied unless she has the last word. [ Late 1800s ]
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A conclusive or authoritative statement or treatment; also, the power or authority of ultimate decision. For example, This report is considered to be the last word on genetic counseling, or In financial matters, the treasurer has the last word. [ Late 1800s ]
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The latest thing; the newest, most fashionable of its kind. For example, Our food processor is the last word in kitchen gadgetry. [ c. 1930 ]