The Collaborative International Dictionary of English v.0.48:

Flume \Flume\ (f;[=u]m), n. [Cf. OE. flum river, OF, flum, fr.
   L. flumen, fr. fluere to flow. [root]84. See Fluent.]
   A stream; especially, a passage channel, or conduit for the
   water that drives a mill wheel; or an artifical channel of
   water for hydraulic or placer mining; also, a chute for
   conveying logs or lumber down a declivity.
   [1913 Webster]

WordNet (r) 3.0 (2006):

flume
    n 1: a narrow gorge with a stream running through it [syn:
         gulch, flume]
    2: watercourse that consists of an open artificial chute filled
       with water for power or for carrying logs

Moby Thesaurus II by Grady Ward, 1.0:

131 Moby Thesaurus words for "flume":
   abysm, abyss, aqueduct, arroyo, avenue, bed, blowhole, box canyon,
   breach, break, canal, canyon, cavity, channel, chap, chasm, check,
   chimney, chink, chute, cleft, cleuch, clough, col, coulee, couloir,
   crack, cranny, creek bed, crevasse, crevice, culvert, cut, cwm,
   debouch, defile, dell, dike, ditch, donga, door, draw, dry bed,
   egress, emunctory, escape, estuary, excavation, exhaust, exit,
   fault, fissure, flaw, floodgate, fracture, furrow, gap, gape, gash,
   gorge, groove, gulch, gulf, gully, gullyhole, headrace, hole,
   incision, irrigation ditch, joint, kloof, leak, loophole, moat,
   notch, nullah, opening, out, outcome, outfall, outgate, outgo,
   outlet, pass, passage, pore, port, race, ravine, rent, rift, rime,
   river bed, riverway, runnel, rupture, sally port, scissure, seam,
   slit, slot, sluice, spillbox, spillway, spiracle, split, spout,
   stream bed, streamway, swash, swash channel, tailrace, tap, trench,
   valley, vent, ventage, venthole, void, vomitory, wadi,
   water carrier, water channel, water furrow, water gap, water gate,
   watercourse, waterway, waterworks, way out, weir