What is Basilica?

Legal Definition
The Latin word basilica (derived from Greek βασιλικὴ στοά, lit. "royal stoa", serving as the tribunal chamber of a king) has three distinct applications in modern English. The word was originally used to describe an ancient Roman public building where courts were held, as well as serving other official and public functions. To a large extent these were the town halls of ancient Roman life. The basilica was centrally located in every Roman town, usually adjacent to the main forum. These buildings, an example of which is the Basilica Ulpia, were rectangular, and often had a central nave and aisles, usually with a slightly raised platform and an apse at each of the two ends, adorned with a statue perhaps of the emperor, while the entrances were from the long sides.

By extension the name was applied to Christian churches which adopted the same basic plan and it continues to be used as an architectural term to describe such buildings, which form the majority of church buildings in Western Christianity, though the basilican building plan became less dominant in new buildings from the later 20th century. Later, the term came to refer specifically to a large and important Roman Catholic church that has been given special ceremonial rights by the Pope.

Roman Catholic basilicas are Catholic pilgrimage sites, receiving tens of millions of visitors per year. In December 2009 the Basilica of Our Lady of Guadalupe in Mexico City set a new record with 6.1 million pilgrims during Friday and Saturday for the anniversary of Our Lady of Guadalupe.
-- Wikipedia
Legal Definition
Civil law. This is derived from a Greek word, which signifies imperial constitutions. The emperor Basilius, finding the Corpus Juris Civilis of Justinian too long and obscure, resolved to abridge it, and under his auspices the work proceeded to the fortieth book, which, at his death, remained unfinished. His son and successor, Leo, the philosopher, continued the work, and published it in sixty books, about the year 880. Constantine Porphyro-genitus, younger brother of Leo, revised the work, re-arranged it, and republished it, Anno Domini, 910. From that time the laws of Justinian ceased to have any force in the eastern empire, and the Basilica were the foundation of the law observed there till Constantine XIII, the last of the Greek emperors, under whom, in 1453, Constantinople was taken by Mahomet the Turk, who put an end to the empire and its laws. Histoire de la Jurisprudence Etienne, Intr. a 1'etude du Droit Romain, §LIII. The Basilica were written in Greek. They were translated into Latin by J. Cujas (Cujacius) Professor of Law in the University of Bourges, and published at Lyons, 22d of January, 1566, in one vol. fo.
-- Bouviers Law Dictionary
Legal Definition
The name given to a compilation of Roman and Greek law, prepared about A. D. 880 by the Emperor Basilius, and published by his successor, Leo the Philosopher. It was written in Greek, was mainly an abridgment of Justinian's Corpus Juris, and comprised sixty books, only a portion of which are extant It remained the law of the Eastern Empire until the fall of Co.nstantinople, in 1453.
-- Black's Law Dictionary
Legal Definition
The Byzantine Code adapted from the Code of Justinian.
-- Ballentine's Law Dictionary