/ Dictionary / Index I isarithm: Meaning and Definition of Find definitions for: i•sa•rithm Pronunciation: (ī'su-ri"um), [key] — n. isopleth. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: isarithm (Thesaurus) Isar isatin Related Content Daily Word Quiz: spectral Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language