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.