A·tom·ic A·tom·ic·al a.
 1. Of or pertaining to atoms.
 2. Extremely minute; tiny.
 Atomic bomb, see atom bomb in the vocabulary.
 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.
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 At·om·ism n.  The doctrine of atoms. See Atomic philosophy, under Atomic.
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 Ep·i·cu·re·an a.
 1. Pertaining to Epicurus, or following his philosophy. “The sect Epicurean.”
 2. Given to luxury; adapted to luxurious tastes; luxurious; pertaining to good eating.
    Courses of the most refined and epicurean dishes.   --Prescott.
 Epicurean philosophy. See Atomic philosophy, under Atomic.