adj. Of an element, consisting of a single atom in the molecule; for example: the noble gases. Note: strictly speaking, a molecule has at least two atoms.
the GNU version of the Collaborative International Dictionary of English
ad. Consisting of, or containing, one atom.
ad. Having the equivalence or replacing power of an atom of hydrogen; univalent.
The Century Dictionary and Cyclopedia
Having the same valence or atomicity as hydrogen, represented by unity.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. of or relating to an element consisting of a single atom
Word Usage
"Ionization was also observed in monatomic inert gases, which proves that the unit of electric charge is a constituent of the atom that is liberated from it by ionization."