Mantra

Potent vibratory chant. The literal translation of Sanskrit mantra is “instrument of thought,” signifying the ideal, inaudible sounds which represent one aspect of creation; when vocalized as syllables, a mantra constitutes a universal terminology. The infinite powers of sound derive from AUM, the “Word” or creative hum of the Cosmic Motor. (1)

References
  1. Autobiography of a Yogi, Paramhansa Yogananda