(Hinduism, Buddhism) A sacred, mystical syllable used in prayer and meditation.

(intransitive) To chant the sacred syllable om.

(colloquial) Clipping of nom.

(politics) Initialism of Occupy movement. / (Commonwealth of Nations, UK) Initialism of Order of Merit. (a dynastic order of the Royal House of Windsor)

(aviation) Initialism of outer marker. / (medicine) Initialism of otitis media. / Initialism of old measurement. / (CB radio slang) Initialism of old man (term of address for a male).

A mass of something.

(biology) The complete whole of a class of substances for a species or an individual.

plural of om

Third-person singular simple present indicative form of om

(US, space science) Orbital Maneuvering System — NASA terminology for orbital maneuvering rockets