clincher

Plural: clinchers

Noun

• A decisive argument or fact that settles a matter.
• an argument that is conclusive
• a point or fact or remark that settles something conclusively
• a tool used to clinch nails or bolts or rivets
• That which clinches; that which makes something final or firm; a decisive factor.
• A tyre with a bead around the edge to attach to the rim of the wheel when inflated.

Examples

• The bingo ’QUIZZES’ was the CLINCHER that sealed his victory in Scrabble.
• The clincher was that we couldn't wait any longer to leave, or it would get dark.

Synonyms

decisive factor, determiner, determining factor