(sinch) noun U.S.
1. A saddle girth, as of horsehair.
2. Colloq. A tight grip.
3. Slang A sure thing; a certainty.
4. Slang An easy thing to do.
—v.t.
1. To fasten a saddle girth around.
2. Slang To get a tight hold upon; make sure of.
—v.i.
3. To tighten a saddle girth: often with up. [<Sp. cincha girth <L cingula girdle <cingere bind]

(sinch) noun
A game of cards in which the five of trumps is the most important card. [Prob. <Sp. cinco five]