index (general term; also before a court of justice): accusator (general term for accuser before a court of justice): delator (an informer, especially a secret informer; such as were common under the emperors): calumniator (a slanderous informer). By means of informers, per indicium: to be a common informer, delationes factitare, or accusationes exercere (to follow the profession of an informer, Tac., Hist., 2, 10, 2, and 5).