I. ˈsinch noun
Etymology: Spanish cincha, from Latin cingula girdle, girth, from cingere — more at cincture
Date: 1859
1. : a girth for a pack or saddle
2. : a tight grip
3.
a. : a thing done with ease
b. : a certainty to happen
it's a cinch he'll break the record
II. verb
Date: 1866
transitive verb
1.
a. : to put a cinch on
b. : to fasten (as a belt or strap) tightly
2. : to make certain : assure
the goal that cinch ed the victory
intransitive verb
: to tighten the cinch — often used with up