The Collaborative International Dictionary of English v.0.48:

Smooth \Smooth\, v. t. [imp. & p. p. Smoothed (sm[=oo]thd); p.
   pr. & vb. n. Smoothing.] [OE. smothen, smethen, AS.
   sm[=e][eth]ian; cf. LG. sm["o]den. See Smooth, a.]
   To make smooth; to make even on the surface by any means; as,
   to smooth a board with a plane; to smooth cloth with an iron.
   Specifically:
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   (a) To free from obstruction; to make easy.
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             Thou, Abelard! the last sad office pay,
             And smooth my passage to the realms of day. --Pope.
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   (b) To free from harshness; to make flowing.
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             In their motions harmony divine
             So smooths her charming tones that God's own ear
             Listens delighted.                   --Milton.
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   (c) To palliate; to gloze; as, to smooth over a fault.
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   (d) To give a smooth or calm appearance to.
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             Each perturbation smoothed with outward calm.
                                                  --Milton.
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   (e) To ease; to regulate. --Dryden.
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The Collaborative International Dictionary of English v.0.48:

Smoothing \Smooth"ing\, a. & n.
   fr. Smooth, v.
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   Smoothing iron, an iron instrument with a polished face,
      for smoothing clothes; a sadiron; a flatiron.

   Smoothing plane, a short, finely set plane, for smoothing
      and finishing work.
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