A person who informs against or accuses someone, especially one who does so formally or professionally.
From Latin 'delator,' literally 'one who carries/reports.' The term appears in Roman legal texts and was used extensively in medieval and early modern European contexts.
In ancient Rome, professional delators were so feared and hated that emperors eventually had to pass laws against them—false accusation became such a racket that honest citizens lived in terror.
Complete word intelligence in one call. Free tier — 50 lookups/day.