What is Assizes?

Legal Definition
The courts of assize, or assizes (/əˈszɪz/), were periodic courts held around England and Wales until 1972, when together with the quarter sessions they were abolished by the Courts Act 1971 and replaced by a single permanent Crown Court. The assizes exercised both civil and criminal jurisdiction, though most of their work was on the criminal side. The assizes heard the most serious cases, which were committed to it by the quarter sessions (local county courts held four times per year), while the more minor offences were dealt with summarily by justices of the peace in petty sessions (also known as magistrates' courts).

The word assize refers to the sittings or sessions (Old French assises) of the judges, known as "justices of assize", who were judges who travelled across the seven circuits of England and Wales on commissions of "oyer and terminer", setting up court and summoning juries at the various assize towns.
-- Wikipedia
Legal Definition
Sessions of the justices or commissioners of assize. See Assise.
-- Black's Law Dictionary
Legal Definition
Sessions of the judges.
-- Ballentine's Law Dictionary