Breadcrumb Home > Dictionary > Index L litmus: Meaning and Definition of Find definitions for: lit•mus Pronunciation: (lit'mus), [key] — n. a blue coloring matter obtained from certain lichens, esp. Roccella tinctoria. In alkaline solution litmus turns blue, in acid solution, red: widely used as a chemical indicator. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: litmus (Thesaurus) litigious litmus paper ✖ Related Content Daily Word Quiz: donnybrook Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language