The Collaborative International Dictionary of English v.0.48:

Smooth \Smooth\ (sm[=oo][th]), a. [Compar. Smoother
   (sm[=oo][th]"[~e]r); superl. Smoothest.] [OE. smothe,
   smethe, AS. sm[=e][eth]e, sm[oe][eth]e, where [=e], [oe],
   come from an older [=o]; cf. LG. sm["o]de, sm["o]e,
   sm["o]dig; of uncertain origin.]
   1. Having an even surface, or a surface so even that no
      roughness or points can be perceived by the touch; not
      rough; as, smooth glass; smooth porcelain. --Chaucer.
      [1913 Webster]

            The outlines must be smooth, imperceptible to the
            touch, and even, without eminence or cavities.
                                                  --Dryden.
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   2. Evenly spread or arranged; sleek; as, smooth hair.
      [1913 Webster]

   3. Gently flowing; moving equably; not ruffled or obstructed;
      as, a smooth stream.
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   4. Flowing or uttered without check, obstruction, or
      hesitation; not harsh; voluble; even; fluent.
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            The only smooth poet of those times.  --Milton.
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            Waller was smooth; but Dryden taught to join
            The varying verse, the full-resounding line. --Pope.
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            When sage Minerva rose,
            From her sweet lips smooth elocution flows. --Gay.
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   5. Bland; mild; smoothing; fattering.
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            This smooth discourse and mild behavior oft
            Conceal a traitor.                    --Addison.
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   6. (Mech. & Physics) Causing no resistance to a body sliding
      along its surface; frictionless.
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   Note: Smooth is often used in the formation of
         self-explaining compounds; as, smooth-bodied,
         smooth-browed, smooth-combed, smooth-faced,
         smooth-finished, smooth-gliding, smooth-grained,
         smooth-leaved, smooth-sliding, smooth-speaking,
         smooth-woven, and the like.
         [1913 Webster]

   Syn: Even; plain; level; flat; polished; glossy; sleek; soft;
        bland; mild; soothing; voluble; flattering; adulatory;
        deceptive.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Smoother \Smooth"er\, n.
   One who, or that which, smooths.
   [1913 Webster]

WordNet (r) 3.0 (2006):

smoother
    n 1: a power tool used for sanding wood; an endless loop of
         sandpaper is moved at high speed by an electric motor [syn:
         drum sander, electric sander, sander, smoother]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "smoother":
   abradant, abrasive, buff, buffer, burnish, calender, chamois, drag,
   glazer, goose, grader, harrow, iron, lawn-roller, mangle, plane,
   polish, polisher, press, roller, rolling pin, sander, sleeker,
   slicker, smooth, steamroller, trowel, wringer