Source : Webster's Revised Unabridged Dictionary (1913)

Quash \Quash\, v. t. [OF. quasser, F. casser, fr. L. quassare to
   shake, shatter, shiver, v. intens. fr. quatere, quassum, to
   shake, shatter. Cf. {Concussion}, {Discuss}, {Rescue}, and
   also {Quash} to annul.]
   1. To beat down, or beat in pieces; to dash forcibly; to
      crush.

            The whales Against sharp rocks, like reeling
            vessels, quashed, Though huge as mountains, are in
            pieces dashed.                        --Waller.

   2. To crush; to subdue; to suppress or extinguish summarily
      and completely; as, to quash a rebellion.

            Contrition is apt to quash or allay all worldly
            grief.                                --Barrow.

Quash \Quash\, n.
   Same as {Squash}.

Quash \Quash\, v. t. [imp. & p. p. {Quashed}; p. pr. & vb. n.
   {Quashing}.] [OF. quasser, F. casser, fr. L. cassare to
   annihilate, annul, fr. cassus empty, vain, of uncertain
   origin. The word has been confused with L. quassare to shake,
   F. casser to break, which is probably of different origin.
   Cf. {Cashier}, v. t.] (Law)
   To abate, annul, overthrow, or make void; as, to quash an
   indictment. --Blackstone.

Quash \Quash\, v. i.
   To be shaken, or dashed about, with noise.

Source : WordNet®

quash
     v 1: put down by force or intimidation; "The government quashes
          any attempt of an uprising"; "China keeps down her
          dissidents very efficiently"; "The rich landowners
          subjugated the peasants working the land" [syn: {repress},
           {keep down}, {subdue}, {subjugate}, {reduce}]
     2: declare invalid; "The contract was annulled"; "void a plea"
        [syn: {invalidate}, {annul}, {void}, {avoid}, {nullify}]
        [ant: {validate}]