Source : Webster's Revised Unabridged Dictionary (1913)

Solder \Sol"der\, n. [Formerly soder; F. soudure, OF. soudeure,
   fr. OF. & F. souder to solder, L. solidare to fasten, to make
   solid. See {Solid}, and cf. {Sawder}.]
   A metal or metallic alloy used when melted for uniting
   adjacent metallic edges or surfaces; a metallic cement.
   Hence, anything which unites or cements.

   {Hard solder}, a solder which fuses only at a red heat, as
      one composed of zinc and copper, or silver and copper,
      etc.

   {Soft solder}, a solder fusible at comparatively low
      temperatures; as, plumbers' solder, consisting of two
      parts lead and one part tin, is a soft solder.

Solder \Sol"der\, v. t. [imp. & p. p. {Soldered}; p. pr. & vb.
   n. {Soldering}.] [Formerlysoder. See {Solder}, n.]
   1. To unite (metallic surfaces or edges) by the intervention
      of a more fusible metal or metallic alloy applied when
      melted; to join by means of metallic cement.

   2. To mend; to patch up. ``To solder up a broken cause.''
      --Hooker.

Source : WordNet®

solder
     n : an alloy (usually of lead and tin) used when melted to join
         two metal surfaces
     v : join or fuse with solder; "solder these two pipes together"