(1) Sets of syllables and, often, additional Sanskrit words and phrases, all of which represent enlightening speech and which, when repeated, protect the mind from destructive states. While repeating the mantras of a Buddha-figure, one imagines having the abilities to communicate perfectly to everyone the complete means for eliminating suffering and reaching enlightenment. Mantras shape the breath, and consequently the subtle energy-winds, enabling one to bring the winds under control for use in meditation practice. (2) A term used to refer to tantra in general, and synonymous with "secret mantra."
Tibetan: སྔགས། sngags
J. Hopkins: Spell