D defs.my
Entry 2 senses Webster, 1913

Riffle

/(rĭf"f'l)/ · Rif·fle · IPA /ˈɹɪfəl/
01 n. A trough or sluice having cleats, grooves, or steps across the bottom for holding quicksilver and catching particles of gold when auriferou…
  1. 1.
    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.(Mining)
  2. 2.
    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.