[It has been taken for granted that this is a contracted word, from L. solido, and hence written solder. The fact may be doubted; but if true, the settled pronunciation seems to render it expedient to let the contracted orthography remain undisturbed.] To unite and make solid, as metallic substances; to join separate things or parts of the same thing by a metallic substance in a state of fustion, which hardens in cooling, and renders the joint solid.