an amendment to the U.S. Constitution mainly guaranteeing certain protections in criminal cases, specif. the clause protecting persons from being compelled to testify against themselves
See Fifth Amendment in American Heritage Dictionary 4
noun
An amendment to the Constitution of the United States, ratified in 1791, that deals with the rights of accused criminals by providing for due process of law, forbidding double jeopardy, and stating that no person may be forced to testify as a witness against himself or herself.