Source : Webster's Revised Unabridged Dictionary (1913)

Smoothing \Smooth"ing\, a. & n.
   fr. {Smooth}, v.

   {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.

Source : WordNet®

smoothing iron
     n : home appliance consisting of a flat metal base that is
         heated and used to smooth cloth [syn: {iron}]