clincher

• POS: Noun
• HYPHEN: clinch=er

CIDE DICTIONARY

clincher, n. 

•  One who, or that which, clinches; that which holds fast.  Pope.  [1913 Webster]
•  That which ends a dispute or controversy; a decisive argument.  [1913 Webster]

OXFORD DICTIONARY

clincher, n. colloq. a remark or argument that settles a matter conclusively.

THESAURUS

clincher

KO, conclusive argument, coup de grace, crusher, death stroke, deathblow, end-all, ender, final stroke, finisher, finishing stroke, floorer, kayo, kayo punch, knockdown argument, knockout, knockout blow, last dab, quietus, settler, sockdolager, stopper, trump

ROGET THESAURUS

clincher

Confutation

N confutation, refutation, answer, complete answer, disproof, conviction, redargution, invalidation, exposure, exposition, clincher, retort, reductio ad absurdum, knock down argument, tu quoque argument, sockdolager, correction, dissuasion, confuting, confuted capable of refutation, refutable, confutable, defeasible, contravene (counter evidence), condemned on one's own showing, condemned out of one's own mouth, the argument falls to the ground, cadit quaestio, it does not hold water, suo sibi gladio hunc jugulo, his argument was demolished by new evidence.