Definition
To express an opinion or fact so vehemently or frequently that it causes others to doubt its sincerity or truth.
He always says he doesn't care about getting promoted, but I think he's protesting too much.
She keeps emphasizing how much she loves her job, which makes me think she might be protesting too much.
When asked if he had eaten the cookies, he denied it so vehemently that I thought he was protesting too much.