Hardeners rhymes with:
gardener's, gardeners, gardener's, gardeners, gardener's, gardeners, londoners, schuldener's, commissioner's, commissioners, commoners, conditioners, confectioners, coroner's, coroners, examiner's, executioner's, executioners, falconers, fasteners, foreigners, foreigners', fresheners, gardener's, gardeners, listeners, londoners, mariners, openers, parishioners, pensioners, petitioners, practitioners, prisoner's, prisoners, prisoners', probationers, questioners, reasoner's, schuldener's, stationers, sweeteners, vacationers, vacationers'