Definition - Mantra

Mantra : Hinduism A sacred verbal formula repeated in prayer, meditation, or incantation, such as an invocation of a god, a magic spell, or a syllable or portion of scripture containing mystical potentialities. http://www.thefreedictionary.com/mantra
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Mantra : (Sans.) Verses from the Vedic works, used as incantations and charms. By Mantras are meant all those portions of the Vedas which are distinct from the Brahmanas, or their interpretation. http://www.theosociety.org/pasadena/key/key-glo2.htm

Mantra Yoga : the meditation techniques that use a charged word or phrase to focus attention, to activate energy, and to unfold the potentials of consciousness.
http://www.mudrashram.com/glossarypage.html#M

Mantra : A word or phrase which is repeated continually in order to achieve relaxation or meditation. http://www.religioustolerance.org/gl_m.htm

Mantra : A sacred mystic syllable, word or verse used in meditation and japa to quiet the mind, balance the inner bodies and attain other desired aims.
http://www.himalayanacademy.com/resources/books/virtue/SVGlossary.html

Mantra : The sacred name of God given by the guru to the disciple. Repetition of the mantra is japa. http://www.vedanta.org/wiv/glossary/glossary_mr.html

Mantra : The names of God; sacred words or divine sounds invested with the power to protect, purify, and transform the individual who repeats them. A mantra received from an enlightened Master is filled with the power of the Master's attainment.
http://www.siddhayoga.org.in/glossary.html

Mantra : Ritual sound, word or phrase used as a tool to focus and quiet the mind. Mantra is a sound or set of sounds that are believed to have the unique power to restore us to a state of pristine harmony. Sea also Chant. http://www.reiki.nu/treatment/healing/dictionary3/dictionary3.html#M

Mantra : also n. Hinduism & Buddhism The supreme and most sacred syllable, consisting in Sanskrit of the three sounds (a), (u), and (m), representing various fundamental triads and believed to be the spoken essence of the universe. It is uttered as a mantra and in affirmations and blessings. http://www.answers.com/topic/aum

Mantra most popular : Aum : Mystic syllable of Hinduism, identified in the Upanishads as standing for the whole world and its parts, including past, present and future, as well as for Paramatma, the Self of all things. "Aum" is the seed sound, the one undifferentiated primal vibration from which all manifestation issues forth. Associated with Lord Ganesha. Pronounced: "ah" "oo" "mm."
http://www.himalayanacademy.com/resources/books/virtue/SVGlossary.html