nisi prius n[Medieval Latin, unless before, the words introducing a clause in an English writ commanding a sheriff to provide a jury at the Court of Westminster on a certain day unless the judges of assize previously come to the county from which the jury is to be returned]
: a court of record that tries an issue of fact before a jury and a single judge
: trial court
: the proceedings in such a court
: the conducting of jury trials [long-distance travel eliminated the nisi prius practice of the justices "W. J. Brennan, Jr."]
Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.