The DICT Development Group

  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.
     [1913 Webster]
  
     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.
        [1913 Webster]

  soft solder
      n 1: solder that melts at a relatively low temperature