In English law. <A court for the trial of cases of treason and felony. The commissioners of assise and nisi prius are judges selected by the king and appointed and authorized under the great seal, including usually two of the judges at Westminster, and sent out twice a year into most of the counties of England, for the trial (with a jury .of the county) of causes then depending at Westminster, both civil and criminal. They sit by virtue of several commissions, each of which, in reality, constitutes them a separate and distinct court. The commission of oyer and terminer gives them authority for the trial of treasons and felonies; that of general gaol delivery empowers them to try every prisoner then in gaol for whatever offense; so that, altogether, they possess full criminal jurisdiction.