SUBATOMIC

subatomic

(adjective) of smaller than atomic dimensions

subatomic

(adjective) of or relating to constituents of the atom or forces within the atom; “subatomic particles”; “harnessing subatomic energy”

Source: WordNet® 3.1

Etymology

Adjective

subatomic (not comparable)

(physics) Relating to particles that are constituents of the atom, or are smaller than an atom; such as proton, neutron, electron, etc.

Relating to any length or mass that is smaller in scale than a the diameter of a hydrogen atom.

Source: Wiktionary