1. [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.
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.
Litmus paper (Chem.), unsized paper saturated with blue or
red litmus, -- used in testing for acids or alkalies.
WordNet (r) 3.0 (2006):
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