take the fifth {v. phr.}, {informal} 1. Taking refuge behind the Fifth Amendment of the Constitution of the United States which guarantees any witness the right not to incriminate himself while testifying at a trial. * /Alger Hiss took the Fifth when asked whether he was a member of the Communist Party./ 2. Not to answer any question in an informal setting. * /Have you been married before? - I take the Fifth./