Fifth Amendment, theˌFifth Aˈmendment, the 
1a part of the constitution of the united states which states that you do not have to give information in a court of law which could be used against you, and that you cannot be put in prison or have your property taken away without a proper legal trial2plead/take the Fifth (Amendment) to refuse to give information against yourself in a court of law. People in the US sometimes use this expression humorously when they do not want to answer a question: 
‘I plead the Fifth’, Jack said, when his wife wanted to know where he had been.
1a part of the constitution of the united states which states that you do not have to give information in a court of law which could be used against you, and that you cannot be put in prison or have your property taken away without a proper legal trial2plead/take the Fifth (Amendment) to refuse to give information against yourself in a court of law. People in the US sometimes use this expression humorously when they do not want to answer a question: ‘I plead the Fifth’, Jack said, when his wife wanted to know where he had been.