The Collaborative International Dictionary of English v.0.48:

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[aum]lla to weld, uppv[aum]lla to boil up, to spring up,
   Dan. v[ae]lde to gush, G. wellen to weld. See Well to
   spring.]
   [1913 Webster]
   1. To press or beat into intimate and permanent union, as two
      pieces of iron when heated almost to fusion.
      [1913 Webster]

   Note: Very few of the metals, besides iron and platinum. are
         capable of being welded. Horn and tortoise shell
         possess this useful property.
         [1913 Webster]

   2. Fig.: To unite closely or intimately.
      [1913 Webster]

            Two women faster welded in one love.  --Tennyson.
      [1913 Webster]

WordNet (r) 3.0 (2006):

welding
    n 1: fastening two pieces of metal together by softening with
         heat and applying pressure