Webster's Revised Unabridged Dictionary · 1913

Sinch

Sinch , noun

[See Cinch.]

A saddle girth made of leather, canvas, woven horsehair, or woven grass. [Western United States]

Sinch , transitive verb

To gird with a sinch; to tighten the sinch or girth of (a saddle); as, to sinch up a sadle. [Western United States]