/ Dictionary / Index A atomic cocktail: Meaning and Definition of Find definitions for: atom'ic cock'tail Pronunciation: [key] — Informal. Informal. an oral dose of a radioactive substance used in the treatment or diagnosis of cancer. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. atomic clock atomic energy Related Content Daily Word Quiz: pristine Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language