/ Dictionary / Index A atomic weight: Meaning and Definition of Find definitions for: atom'ic weight' Pronunciation: [key] — Chem. Chem. the average weight of an atom of an element, formerly based on the weight of one hydrogen atom taken as a unit or on the weight of an oxygen atom, but after 1961 based on the weight of the carbon-12 atom. Abbr.: at. wt. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. atomic volume atomism Related Content Daily Word Quiz: crutiny Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language