Informer

Part of speech: noun (n.)

1. One who informs, animates, or inspires. [Obs.] Thomson. Nature, informer of the poet's art. Pope.

2. One who informs, or imparts knowledge or news.

3. One who informs a magistrate of violations of law; one who informs against another for violation of some law or penal statute. Common informer (Law), one who habitually gives information of the violation of penal statutes, with a view to a prosecution therefor. Bouvier. Wharton.