(rif′əl) noun
1. U.S. A shoal or rocky obstruction lying beneath the surface of a river or other stream.
2. A stretch of shallow, choppy water caused by such a shoal; a rapid.
3. A way of shuffling cards.
—v.t. & v.i. ·fled, ·fling
1. To cause or form a rapid.
2. To shuffle (cards) by bending up adjacent corners of two halves of the pack, and permitting the cards to slip together as they are released.
3. To thumb through (the pages of a book). [? Blend of RIPPLE and RUFFLE]

(rif′əl) noun Mining
1. A groove or indentation set in the bottom of an inclined trough or sluice, for arresting gold contained in sands or gravels.
2. A cross slat or cleat rising above the bottom of such a sluice and adapted for catching gold: also riffle bar, riffle block. [Cf. LG riffel furrow]