At"om (?), n. [L. atomus, Gr. ?,
uncut, indivisible; 'a priv. + ?, verbal adj. of ? to cut:
cf. F. atome. See Tome.] 1. (Physics)
(a) An ultimate indivisible particle of matter.
(b) An ultimate particle of matter not necessarily
indivisible; a molecule. (c) A constituent
particle of matter, or a molecule supposed to be made up of subordinate
particles.
☞ These three definitions correspond to different views of the
nature of the ultimate particles of matter. In the case of the last two,
the particles are more correctly called molecules. Dana.
2. (Chem.) The smallest particle of matter
that can enter into combination; one of the elementary constituents of a
molecule.
3. Anything extremely small; a particle; a
whit.
There was not an atom of water.
Sir J. Ross.
At"om, v. t. To reduce to atoms.
[Obs.] Feltham.