/ Dictionary / Index M mantissa: Meaning and Definition of Find definitions for: man•tis•sa Pronunciation: (man-tis'u), [key] — n. the decimal part of a common logarithm. Cf.(def. 3a). an addition of little or no importance, as to a literary work. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mantissa (Thesaurus) mantispid mantis shrimp Related Content Daily Word Quiz: placid Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language