WordWeb Online

1. Immeasurably small
    
2. Of or relating to or comprising atoms
   "atomic structure"; "atomic hydrogen"
    
3. (weapons) deriving destructive energy from the release of atomic energy
   "atomic bombs";
   - nuclear
    
4. Unable to be split or made any smaller
   "A bit is an atomic item of data"

See also: little, small, thermonuclear

Antonym: conventional

Encyclopedia: Atomic, biological and chemical warfare