Source : Webster's Revised Unabridged Dictionary (1913)

Soldering \Sol"der*ing\,
   a. & n. from {Solder}, v. t.

   {Soldering iron}, {Soldering tool}, an instrument for
      soldering, consisting of a bit or bolt of copper having a
      pointed or wedge-shaped end, and furnished with a handle.

Source : WordNet®

soldering iron
     n : a hand tool with a heatable tip; used to melt and apply
         solder