/ Dictionary / Index S sesqui-: Meaning and Definition of Find definitions for: sesqui- Pronunciation: [key] a combining form meaning “one and a half,” used in the formation of compound words: sesquicentennial. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Sesotho sesquicarbonate Related Content Daily Word Quiz: abstain Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language