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Wordnet 3.0

NOUN (1)

1. a coloring material (obtained from lichens) that turns red in acid solutions and blue in alkaline solutions; used as a very rough acid-base indicator;
[syn: litmus, litmus test]


The Collaborative International Dictionary of English v.0.48:

Litmus \Lit"mus\, n. [D. lakmoes; lak lacker + moes a thick preparation of fruit, pap, prob. akin to E. meat: cf. G. lackmus. See Lac a resinous substance.] (Chem.) A dyestuff extracted from certain lichens (Roccella tinctoria, Lecanora tartarea, etc.), as a blue amorphous mass which consists of a compound of the alkaline carbonates with certain coloring matters related to orcin and orcein. [1913 Webster] Note: Litmus is used as a dye, and being turned red by acids and restored to its blue color by alkalies, is a common indicator or test for acidity and alkalinity. [1913 Webster] Litmus paper (Chem.), unsized paper saturated with blue or red litmus, -- used in testing for acids or alkalies. [1913 Webster]
WordNet (r) 3.0 (2006):

litmus n 1: a coloring material (obtained from lichens) that turns red in acid solutions and blue in alkaline solutions; used as a very rough acid-base indicator [syn: litmus, litmus test]