The Collaborative International Dictionary of English v.0.48:

Sluice \Sluice\, n. [OF. escluse, F. ['e]cluse, LL. exclusa,
   sclusa, from L. excludere, exclusum, to shut out: cf. D.
   sluis sluice, from the Old French. See Exclude.]
   1. An artifical passage for water, fitted with a valve or
      gate, as in a mill stream, for stopping or regulating the
      flow; also, a water gate or flood gate.
      [1913 Webster]

   2. Hence, an opening or channel through which anything flows;
      a source of supply.
      [1913 Webster]

            Each sluice of affluent fortune opened soon.
                                                  --Harte.
      [1913 Webster]

            This home familiarity . . . opens the sluices of
            sensibility.                          --I. Taylor.
      [1913 Webster]

   3. The stream flowing through a flood gate.
      [1913 Webster]

   4. (Mining) A long box or trough through which water flows,
      -- used for washing auriferous earth.
      [1913 Webster]

   Sluice gate, the sliding gate of a sluice.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sluice \Sluice\, v. t. [imp. & p. p. Sluiced; p. pr. & vb. n.
   Sluicing.]
   1. To emit by, or as by, flood gates. [R.] --Milton.
      [1913 Webster]

   2. To wet copiously, as by opening a sluice; as, to sluice
      meadows. --Howitt.
      [1913 Webster]

            He dried his neck and face, which he had been
            sluicing with cold water.             --De Quincey.
      [1913 Webster]

   3. To wash with, or in, a stream of water running through a
      sluice; as, to sluice eart or gold dust in mining.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sluice
    n 1: conduit that carries a rapid flow of water controlled by a
         sluicegate [syn: sluice, sluiceway, penstock]
    v 1: pour as if from a sluice; "An aggressive tide sluiced
         across the barrier reef" [syn: sluice, sluice down]
    2: irrigate with water from a sluice; "sluice the earth" [syn:
       sluice, flush]
    3: transport in or send down a sluice; "sluice logs"
    4: draw through a sluice; "sluice water"

Moby Thesaurus II by Grady Ward, 1.0:

163 Moby Thesaurus words for "sluice":
   aboideau, air lock, aqueduct, arroyo, avenue, baptize, bath, bathe,
   bed, blow out, blowhole, canal, channel, chute, cloaca,
   cloaca maxima, creek bed, culvert, debouch, deluge, dip, dock gate,
   donga, door, douche, douse, drain, drain out, drench, drown,
   dry bed, duck, dunk, egress, empty, emunctory, escape, estuary,
   exhaust, exit, find vent, float, flood, flood-hatch, floodgate,
   flow, flow on, flow out, flume, flush, flush out, gargle, gate,
   gulch, gully, gullyhole, gush, gush out, gutter, head gate,
   headchute, headrace, holystone, inundate, irrigate,
   irrigation ditch, jet, kennel, lather, launder, lave, lock,
   lock gate, loophole, mop, mop up, nullah, opening, out, outcome,
   outfall, outflow, outgate, outgo, outlet, outpour, penstock,
   piscina, pore, port, pour, pour on, pour out, race, rain, rinse,
   rinse out, ritually immerse, river bed, riverway, roll, run out,
   runnel, sally port, scour, scrub, scrub up, scupper, sewer,
   shampoo, shower, sink, sluice gate, sluice out, soak, soap, sough,
   spew out, spillbox, spillway, spiracle, sponge, spout, spout out,
   spurt, stream, stream bed, streamway, submerge, sump, surge, swab,
   swamp, swash, swash channel, syringe, tailrace, tap, tide gate,
   toivel, tub, vent, ventage, venthole, vomit forth, vomitory, wadi,
   wash, wash out, wash up, water carrier, water channel,
   water furrow, water gap, water gate, watercourse, waterway,
   waterworks, way out, weir, well, well out, whelm