Source : Webster's Revised Unabridged Dictionary (1913)

Cinch \Cinch\, v. t. [imp. & p. p. {Cinched}; p. pr. & vb. n.
   {Cinch"ing}.]
   1. To put a cinch upon; to girth tightly. [Western U. S.]

   2. To get a sure hold upon; to get into a tight place, as for
      forcing submission. [Slang, U. S.]