Source : Webster's Revised Unabridged Dictionary (1913)

Weld \Weld\, v. t. [imp. & p. p. {Welded}; p. pr. & vb. n.
   {Welding}.] [Probably originally the same word as well to
   spring up, to gush; perhaps from the Scand.; cf. Sw. v["a]lla
   to weld, uppv["a]lla to boil up, to spring up, Dan. v[ae]lde
   to gush, G. wellen to weld. See {Well} to spring.]
   1. To press or beat into intimate and permanent union, as two
      pieces of iron when heated almost to fusion.

   Note: Very few of the metals, besides iron and platinum. are
         capable of being welded. Horn and tortoise shell
         possess this useful property.

   2. Fig.: To unite closely or intimately.

            Two women faster welded in one love.  --Tennyson.

Source : WordNet®

welding
     n : fastening two pieces of metal together by softening with
         heat and applying pressure