/ Dictionary / Index D diabase: Meaning and Definition of Find definitions for: di•a•base Pronunciation: (dī'u-bās"), [key] — n. Petrol. a fine-grained gabbro occurring as minor intrusions. a dark igneous rock consisting essentially of augite and feldspar; an altered dolerite. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. dia- diabatic Related Content Daily Word Quiz: soporific Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language