clincher > define

noun

• An argument that is conclusive.
  • synonyms: determiner, determining factor
• A point or fact or remark that settles something conclusively.
  • synonyms: decisive factor
• A tool used to clinch nails or bolts or rivets. .

• (n.) That which ends a dispute or controversy; a decisive argument.
• (n.) One who or that which, clinches; that which holds fast.