litmus test

noun

1. Chemistry.,  the use of litmus paper or solution to test the acidity or alkalinity of a solution.

2. a crucial and revealing test in which there is one decisive factor.

litmus test

noun

1. a test to establish the acidity or alkalinity of a mixture

2. a critical indication of future success or failure

Word History and Origins

Origin of litmus test¹

First recorded in 1955–60; so called from chemical tests in which litmus or litmus paper is an indicator