The sum total of all energy; the first cause; all-pervading sound.
Om (or Auṃ [ə̃ũ], Sanskrit: ॐ) is a sacred sound and a spiritual icon in Dharmic religions. It is also a mantra in Hinduism, Buddhism and Jainism. In Hinduism, Om is a spiritual symbol (pratima) referring to Atman (soul, self within) and Brahman (ultimate reality, entirety of the universe, truth, divine, supreme spirit, cosmic principles, knowledge).
The syllable is one of the most important symbols in Hinduism, and is often found at the beginning and the end of chapters in the Vedas, the Upanishads, and other Hindu texts. It is a sacred spiritual incantation made before and during the recitation of spiritual texts, during puja and private prayers, in ceremonies of rites of passages (sanskara) such as weddings, and sometimes during meditative and spiritual activities such as Yoga.
Om is part of the iconography found in ancient and medieval era temples, monasteries and spiritual retreats in Hinduism, Buddhism and Jainism. A related symbol Ik Onkar is also found in Sikhism. The symbol has a spiritual meaning in all Indian religions, but the meaning and connotations of Om vary between the diverse schools within and across the various traditions.
The syllable is also referred to as omkara (oṃkāra), aumkara (auṃkāra), and pranava (praṇava).
Example via www.ramdass.org: Mantras
Example via www.mindpodnetwork.com: The Mind & The Heart