From Longman Dictionary of Contemporary Englishsomebody/something is the exception that proves the rulesomebody/something is the exception that proves the rulespoken used to say that the fact that something is not true or does not exist in one situation emphasizes the fact that it is true or exists in general Most people here are very dedicated; I’m afraid Rhea’s the exception that proves the rule. → exception
Examples from the Corpus
somebody/something is the exception that proves the rule• Most people our age have finished school, and Mike is the exception that proves the rule. 