Source : Webster's Revised Unabridged Dictionary (1913)

Clinch \Clinch\ (kl[i^]nch; 224), v. t. [imp. & p. p.
   {Clinched}; p. pr. & vb. n. {Clinching}.] [OE. clenchen,
   prop. causative of clink to cause to clink, to strike; cf. D.
   klinken to tinkle, rivet. See {Clink}.]
   1. To hold firmly; to hold fast by grasping or embracing
      tightly. ``Clinch the pointed spear.'' --Dryden.

   2. To set closely together; to close tightly; as, to clinch
      the teeth or the first. --Swift.

   3. To bend or turn over the point of (something that has been
      driven through an object), so that it will hold fast; as,
      to clinch a nail.

   4. To make conclusive; to confirm; to establish; as, to
      clinch an argument. --South.

Source : WordNet®

clinched
     adj : closed or squeezed together tightly; "a clenched fist"; "his
           clenched (or clinched) teeth" [syn: {clenched}]