1. The repetition of a mantra or name of God as a form of devotion, honor, or to induce an altered state. Note that some people conflate the concept of a mantra with that of japa. Japa may be performed out loud, quietly, silently but with the moving of the lips, or just in the mind.
2. Sanskrit. Constant repetition (silently or audibly) of an affirmative mantra to drive it deeply into the subconscious mind.