Mantra

Webster's Dictionary

(n.) A prayer; an invocation; a religious formula; a charm.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature

a secret, the communication of which forms the chief ceremony of initiation in all Hindu sects. It generally consists of the name of some deity, or a short address to him; it is conveyed by the teacher to the disciple in a whisper, and when once known, is carefully concealed from all the uninitiated. The word mantra is also employed generally to denote a spell or enchantment, and also a hymn or a prayer.

The Nuttall Encyclopedia

The name given to hymns from the Veda, the repetition of which are supposed to have the effect of a charm.