faithlessEnglishOxford New American Dictionaryfaithless /ˈfāTHləs, ˈfeɪθləs / ▸ adjective 1 disloyal, especially to a spouse or partner; untrustworthy: her faithless lover. 2 without religious faith: they were ungodly and faithless. – DERIVATIVES faithlessly ,faithlessness /ˈfāTHləsnəs, ˈfeɪθləsnəs / noun