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Related to litmus: litmus paper
1. A chemical test used to determine acidity or alkalinity in a solution. The students performed a litmus test in class to learn whether the chemical solution was an acid or a base.
2. A test used to determine someone's true intentions or beliefs. I used his reaction to my favorite movie as a litmus test to determine if he was worth dating.
1. Lit. a test used to determine the acidity or alkalinity of chemical substances. (Acid turns litmus paper red and alkaline compounds turn it blue.) I used a litmus test to show that the compound was slightly acid.
2. Fig. a question or experiment that seeks to determine the state of one important factor. His performance on the long exam served as a litmus test to determine whether he would go to college. The amount of white cells in my blood became the litmus test for diagnosing my disease.
a litmus test
something that shows clearly what someone's opinions or intentions are
Usage notes: Litmus is a substance used in chemical tests because it changes colour.His views on abortion are effectively a litmus test of his views on women's rights.