/ Dictionary / Index S sesquicarbonate: Meaning and Definition of Find definitions for: ses•qui•car•bon•ate Pronunciation: (ses"kwi-kär'bu-nāt", -nit), [key] — n. Chem. a salt intermediate in composition between a carbonate and a bicarbonate or consisting of the two combined. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. sesqui- sesquicentennial Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language