clincher

Etymology
From.

Noun

 * 1) That which clinches; that which makes something final or firm; a decisive factor.
 * The clincher was that we couldn't wait any longer to leave, or it would get dark.
 * 1)  A tyre with a bead around the edge to attach to the rim of the wheel when inflated.
 * 1)  A tyre with a bead around the edge to attach to the rim of the wheel when inflated.
 * 1)  A tyre with a bead around the edge to attach to the rim of the wheel when inflated.

Etymology
or.

Noun

 * 1) clinker