Source : Webster's Revised Unabridged Dictionary (1913)

Riffle \Rif"fle\, n. [CF. G. riffeln, riefeln, to groove. Cf.
   {Rifle} a gun.] (Mining)
   A trough or sluice having cleats, grooves, or steps across
   the bottom for holding quicksilver and catching particles of
   gold when auriferous earth is washed; also, one of the
   cleats, grooves, or steps in such a trough. Also called
   ripple.

Riffle \Rif"fle\, n. [Cf. {Riffle} a trough.]
   A ripple in a stream or current of water; also, a place where
   the water ripples, as on a shallow rapid. [Local, U. S.]

         The bass have left the cool depth beside the rock and
         are on the riffle or just below it.      --James A.
                                                  Henshall.

Source : WordNet®

riffle
     n 1: a small wave on the surface of a liquid [syn: {ripple}, {rippling},
           {wavelet}]
     2: shuffling by splitting the pack and interweaving the two
        halves at their corners
     v 1: twitch or flutter; "the paper flicked" [syn: {flick}, {ruffle}]
     2: look through a book or other written material; "He thumbed
        through the report"; "She leafed through the volume" [syn:
         {flick}, {flip}, {thumb}, {leaf}, {riff}]
     3: stir up (water) so as to form ripples [syn: {ripple}, {ruffle},
         {cockle}, {undulate}]
     4: shuffle (playing cards) by separating the deck into two
        parts and riffling with the thumbs so the cards intermix