Breadcrumb Home > Dictionary > Index A Cite atomic theory: Meaning and Definition of Find definitions for: atom'ic the'ory Pronunciation: [key] any of several theories describing the structure, behavior, and other properties of the atom and its component parts. atomism (def. 1). Random House Unabridged Dictionary, Copyright 1997, by Random House, Inc., on Infoplease. atomic structure atomic unit of length TrendingHere are the facts and trivia that people are buzzing about. February 2021 Current Events: US News The Berlin Conference and the Partition of Africa The Implied Powers of Congress Noble Titles and Ranks in a Monarchy Keeping Your Brain Active in a COVID-19 World The Manchu Related Content Daily Word Quiz: invective Analogy of the Day: Today?s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language