or clencher, subs. (colloquial).—1.  That which decides a matter, especially a retort which closes an argument; a ‘finisher,’ ‘settler,’ ‘corker.’ [From CLINCH, ‘to secure or make fast,’ through its obsolete meaning of ‘to pun or quibble,’ + ER.]

1

  1754.  B. MARTIN, English Dictionary. CLINCHER … an unanswerable reason or argument.

2

  1839.  P. EGAN, Finish to Life in London, p. 13.

        Death comes but once, the Philosophers say,
    And ’tis true, my brave boys, but that once is a CLENCHER;
It takes us from drinking and loving away,
    And spoils at a blow the best tippler and wencher!

3

  1836.  DICKENS, Pickwick Papers, ch. xvi., p. 136. ‘Why cannot I communicate with the young lady’s friends?’ ‘Because they live one hundred miles from here, sir,’ responded Job Trotter. ‘That’s a CLINCHER,’ said Mr. Weiler, aside.

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  2.  (common).—An unsurpassed lie; a ‘stopper-up.’ [This sense flows naturally from sense 1 and the accepted usages of CLINCH, verb and noun. Cf., CLINKER, WHOPPER, THUMPER, WHACKER, etc.] For synonyms, see WHOPPER.

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