subatomic UK /ˌsʌbəˈtɒmɪk/US /ˌsʌbəˈtɑːmɪk/ adjective2 •Relating to particles that are constituents of the atom, or are smaller than an atom; such as proton, neutron, electron, etc. •Relating to something that is smaller in scale than the diameter of a hydrogen atom.The electron microscope is able to resolve detail at the subatomic level.
