The Collaborative International Dictionary of English v.0.48:

Feeder \Feed"er\, n.
   1. One who, or that which, gives food or supplies
      nourishment; steward.
      [1913 Webster]

            A couple of friends, his chaplain and feeder.
                                                  --Goldsmith.
      [1913 Webster]

   2. One who furnishes incentives; an encourager. "The feeder
      of my riots." --Shak.
      [1913 Webster]

   3. One who eats or feeds; specifically, an animal to be fed
      or fattened.
      [1913 Webster]

            With eager feeding, food doth choke the feeder.
                                                  --Shak.
      [1913 Webster]

   4. One who fattens cattle for slaughter.
      [1913 Webster]

   5. A stream that flows into another body of water; a
      tributary; specifically (Hydraulic Engin.), a water course
      which supplies a canal or reservoir by gravitation or
      natural flow.
      [1913 Webster]

   6. A branch railroad, stage line, air route, or the like; a
      side line which increases the business of the main line.
      [1913 Webster +PJC]

   7. (Mining)
      (a) A small lateral lode falling into the main lode or
          mineral vein. --Ure.
      (b) A strong discharge of gas from a fissure; a blower.
          --Raymond.
          [1913 Webster]

   8. (Mach.) An auxiliary part of a machine which supplies or
      leads along the material operated upon.
      [1913 Webster]

   9. (Steam Engine) A device for supplying steam boilers with
      water as needed.
      [1913 Webster]

WordNet (r) 3.0 (2006):

feeder
    n 1: an animal being fattened or suitable for fattening
    2: someone who consumes food for nourishment [syn: eater,
       feeder]
    3: a branch that flows into the main stream [syn: feeder,
       tributary, confluent, affluent] [ant: distributary]
    4: a machine that automatically provides a supply of some
       material; "the feeder discharged feed into a trough for the
       livestock" [syn: self-feeder, feeder]
    5: an outdoor device that supplies food for wild birds [syn:
       bird feeder, birdfeeder, feeder]
    6: an animal that feeds on a particular source of food; "a bark
       feeder"; "a mud feeder"

Moby Thesaurus II by Grady Ward, 1.0:

165 Moby Thesaurus words for "feeder":
   Brillat-Savarin, L, Lucullus, Roscius, actor, actress, affluent,
   antagonist, antihero, bad guy, barnstormer, bayou, billabong, bit,
   bit part, board-and-roomer, boarder, bon vivant, branch,
   cable railway, cannibal, carnivore, cast, character,
   character actor, character man, character woman, child actor,
   cog railway, confluent, confluent stream, connoisseur of food,
   consumer, cue, dendritic drainage pattern, diner, diner-out,
   diseur, diseuse, dramatizer, eater, eater-out, effluent, el,
   electric railway, elevated, elevated railway, embankment, epicure,
   fat part, feeder line, flesh-eater, foil, fork, fruitarian,
   gastronome, glutton, gourmand, gourmet, grain-eater, graminivore,
   granivore, gravity-operated railway, heavy, herbivore, hero,
   heroine, high liver, histrio, histrion, horse railway,
   hungry mouth, ingenue, junction, juvenile, lactovegetarian, lead,
   lead role, leading lady, leading man, leading woman,
   light railroad, line, lines, luncher, main line, man-eater,
   matinee idol, meat-eater, metro, mime, mimer, mimic, monologist,
   monorail, mouth, mummer, omnivore, omophagist, pantomime,
   pantomimist, pantophagist, part, person, personage, phytophage,
   picnicker, piece, plant-eater, playactor, player, predacean, prong,
   protagonist, protean actor, rack railway, rack-and-pinion railway,
   rail, rail line, railroad, railway, reciter, roadbed, roadway,
   role, side, sidetrack, siding, soubrette, stage performer,
   stage player, stooge, straight man, straight part, street railway,
   streetcar line, stroller, strolling player, subway,
   supporting character, supporting role, switchback, terminal,
   terminus, theatrical, thespian, title role, track, tram, tramline,
   trencherman, trestle, tributary, trolley line, trouper, trunk,
   trunk line, tube, turnout, underground, utility man, vegetarian,
   villain, walk-on, walking part