[at.om] n [ME, fr. L atomus, fr. Gk atomos, fr. atomos indivisible, fr. a- + temnein to cut] (15c) 1: one of the minute indivisible particles of which according to ancient materialism the universe is composed
2: a tiny particle: bit
3: the smallest particle of an element that can exist either alone or in combination
4: the atom considered as a source of vast potential energy