/ Dictionary / Index I infinitesimal calculus: Meaning and Definition of Find definitions for: in'finites'imal cal'culus Pronunciation: [key] the differential calculus and the integral calculus, considered together. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. infinitesimal infinitival Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language