- a soluble powder obtained from certain lichens. It turns red under acid conditions and blue under basic conditions and is used as an indicator
WordReference Random House Learner's Dictionary of American English © 2026
lit•mus /ˈlɪtməs/USA pronunciation
n. [uncountable]
WordReference Random House Unabridged Dictionary of American English © 2026- Chemistrycoloring matter that turns blue in alkaline solution and red in acid solution, used as a chemical indicator.
lit•mus
(lit′məs),USA pronunciation n.
- Chemistrya 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.
- Old Norse litmosi dye-moss, equivalent. to lit- color, dye + mosi moss
- earlier lytmos 1495–1505
Collins Concise English Dictionary © HarperCollins Publishers::
litmus /ˈlɪtməs/ n
'litmus' also found in these entries (note: many are not synonyms or translations):
acid
- base
- orchil
- orcinol
- test paper
- alkali
- indicator
- litmus paper
- litmus test
- turnsole