To deny something so often and/or so forcefully that people think one is not telling the truth. Taken from a line in Shakespeare's Hamlet: "Methinks the lady doth protest too much" (and often used in that structure). At even the slightest suggestion that there might be some impropriety in the company's accounts, the manager flies into a rage. He protests a bit too much, don't you think? Shiela mentions at every opportunity how she loves her husband and didn't marry him for his money—methinks she doth protest too much.