Om \Om\, interj. & n. [Also Aum, Um.]

[Skr. [=o]m.]

A mystic syllable or ejaculation used by Hindus and Buddhists in religious rites, -- orig. among the Hindus an exclamation of assent, like Amen, then an invocation, and later a symbol of the trinity formed by Vishnu, Siva, and Brahma.

Om mani padme hun, a sacred formula of buddhism (esp. of the Lamaists) translated ``O, the Jewel in the Lotus, Amen,'' and referring to Amitabha, who is commonly represented as standing or sitting within a lotus.

Source: Webster's Revised Unabridged Dictionary (1913)