Informer
Informer (in*fôrm"ẽr) , noun
[From Inform, v.]
1.
One who informs, animates, or inspires. [Obsolete] — Thomson
Nature, informer of the poet's art.
2.
One who informs, or imparts knowledge or news.
3.
(Law) One who informs a magistrate of violations of law; one who informs against another for violation of some law or penal statute.
Collocations (1)
Common informer (Law) , one who habitually gives information of the violation of penal statutes, with a view to a prosecution therefor. — Bouvier