The Collaborative International Dictionary of English v.0.48:

Runner \Run"ner\, n. [From Run.]
   1. One who, or that which, runs; a racer.
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   2. A detective. [Slang, Eng.] --Dickens.
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   3. A messenger. --Swift.
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   4. A smuggler. [Colloq.] --R. North.
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   5. One employed to solicit patronage, as for a steamboat,
      hotel, shop, etc. [Cant, U.S.]
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   6. (Bot.) A slender trailing branch which takes root at the
      joints or end and there forms new plants, as in the
      strawberry and the common cinquefoil.
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   7. The rotating stone of a set of millstones.
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   8. (Naut.) A rope rove through a block and used to increase
      the mechanical power of a tackle. --Totten.
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   9. One of the pieces on which a sled or sleigh slides; also
      the part or blade of a skate which slides on the ice.
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   10. (Founding)
       (a) A horizontal channel in a mold, through which the
           metal flows to the cavity formed by the pattern;
           also, the waste metal left in such a channel.
       (b) A trough or channel for leading molten metal from a
           furnace to a ladle, mold, or pig bed.
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   11. The movable piece to which the ribs of an umbrella are
       attached.
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   12. (Zool.) A food fish (Elagatis pinnulatus) of Florida
       and the West Indies; -- called also skipjack,
       shoemaker, and yellowtail. The name alludes to its
       rapid successive leaps from the water.
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   13. (Zool.) Any cursorial bird.
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   14. (Mech.)
       (a) A movable slab or rubber used in grinding or
           polishing a surface of stone.
       (b) A tool on which lenses are fastened in a group, for
           polishing or grinding.
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WordNet (r) 3.0 (2006):

runner
    n 1: someone who imports or exports without paying duties [syn:
         smuggler, runner, contrabandist, moon curser,
         moon-curser]
    2: someone who travels on foot by running
    3: a person who is employed to deliver messages or documents;
       "he sent a runner over with the contract"
    4: a baseball player on the team at bat who is on base (or
       attempting to reach a base) [syn: base runner, runner]
    5: a horizontal branch from the base of plant that produces new
       plants from buds at its tips [syn: stolon, runner,
       offset]
    6: a trained athlete who competes in foot races
    7: (football) the player who is carrying (and trying to advance)
       the ball on an offensive play [syn: ball carrier, runner]
    8: a long narrow carpet
    9: device consisting of the parts on which something can slide
       along
    10: fish of western Atlantic: Cape Cod to Brazil [syn: runner,
        blue runner, Caranx crysos]

Moby Thesaurus II by Grady Ward, 1.0:

111 Moby Thesaurus words for "runner":
   Hermes, Iris, Jehu, Mercury, Paul Revere, Pheidippides, Skimobile,
   Sno-Cat, agent, appendage, arm, bine, blade, bough, branch,
   branchedness, branchiness, burgeon, carrier, commissionaire,
   conductor, contrabandist, courier, creeper, deadwood,
   diplomatic courier, driver, emissary, engineer, estafette, express,
   flagellum, flier, fork, frond, functionary, gate, go-between, goer,
   gofer, gunrunner, hand, handler, hell-driver, horse racer, hummer,
   hurdler, hustler, imp, ingate, jockey, jogger, joint, leg, limb,
   link, lobe, lobule, manipulator, member, message-bearer, messenger,
   nuncio, offshoot, operant, operative, operator, organ, page, pilot,
   pinion, post, postboy, postrider, racer, ramage, ramification,
   rumrunner, sarment, scion, scorcher, shoot, sizzler, sled, sleigh,
   slip, smuggler, snowmobile, spear, speed demon, speeder, spray,
   sprig, sprit, sprout, sprue, spur, steersman, stem, stepper,
   stolon, sucker, switch, tail, tedge, tendril, thallus, turfman,
   twig, weasel, wing