de·ca·les·cence (dē'kə-lěs'əns) n. A sudden slowing in the rate of temperature increase in a metal being heated, caused by endothermic structural changes and resulting in a darkening of the metal.
[From de- + Latin calēscere, to become warm, inchoative of calēre, to be warm; see kelə-1 in Indo-European roots.] de'ca·les'cent adj.