nisi prius
/ˌnʌɪsʌɪ ˈprʌɪəs/Law. Now historical
noun
1A writ directing a sheriff to provide a jury at the Court of Westminster on a particular day, unless the assize judges come before that day to the county from which the jury was to be drawn. Now only in writ of nisi prius.
2The hearing of civil causes by the judges in the Assize Court or (in later British use) Crown Court; court business of this kind. Also in cause (also court, justice, record,etc.) of nisi prius.
Origin
Late Middle English; earliest use found in Ordinances Exchequer. From Anglo-Norman and Middle French nisi prius and their etymon post-classical Latin nisi prius from classical Latin nisi prius unless previously from nisi unless + prius before. In phrase writ of nisi prius after Anglo-Norman brief de nisi prius, post-classical Latin breve de nisi prius. With clause of nisi prius compare post-classical Latin clausula de nisi prius.