Source : Webster's Revised Unabridged Dictionary (1913)

Atomic \A*tom"ic\, Atomical \A*tom"ic*al\, a. [Cf. F. atomique.]
   1. Of or pertaining to atoms.

   2. Extremely minute; tiny.

   {Atomic philosophy}, or {Doctrine of atoms}, a system which,
      assuming that atoms are endued with gravity and motion,
      accounted thus for the origin and formation of all things.
      This philosophy was first broached by Leucippus, was
      developed by Democritus, and afterward improved by
      Epicurus, and hence is sometimes denominated the Epicurean
      philosophy.

   {Atomic theory}, or the {Doctrine of definite proportions}
      (Chem.), teaches that chemical combinations take place
      between the supposed ultimate particles or atoms of
      bodies, in some simple ratio, as of one to one, two to
      three, or some other, always expressible in whole numbers.
      

   {Atomic weight} (Chem.), the weight of the atom of an element
      as compared with the weight of the atom of hydrogen, taken
      as a standard.