'litmus test' definitions:

Definition of 'litmus test'

noun

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]

noun

A test that relies on a single indicator; "her litmus test for good breeding is whether you split infinitives"

Definition of 'litmus test'

From: GCIDE

litmus test \litmus test\,
1. (Chem.) A test to determine acidity or alkalinity, using litmus as an inddicator. [PJC]
2. Hence: (Fig.) A test for a single factor, which has only two outcomes, positive or negative; specifically: (Politics) the question of whether a candidate for office is for or against a particular position on an issue; -- used, e.g. by voters concerned predominantly with a single issue, to decide whether to vote for or against a candidate; as, many voters take a candidate's position on abortion as their litmus test. [PJC]