Synonyms and related words :
age, anneal, antiquate, become extinct, become obsolete, calcify, callous, case harden, cornify, date, fade, firm, fust, grow old, harden, indurate, lapidify, lithify, lose currency, molder, obsolesce, ossify, outdate, perish, petrify, rust, steel, superannuate, temper, toughen, vitrify