What is Bishop?

Legal Definition
A bishop (English derivation from the New Testament of the Christian Bible Greek ἐπίσκοπος, epískopos, "overseer", "guardian") is an ordained or consecrated member of the Christian clergy who is generally entrusted with a position of authority and oversight.

Within the Roman Catholic, Eastern Orthodox, Oriental Orthodox, Anglican, Old Catholic and Independent Catholic churches and in the Assyrian Church of the East, bishops claim apostolic succession, a direct historical lineage dating back to the original Twelve Apostles. Within these churches, bishops are seen as those who possess the full priesthood and can ordain clergy – including other bishops. Some Protestant churches including the Lutheran and Methodist churches have bishops serving similar functions as well, though not always understood to be within apostolic succession in the same way. One who has been ordained deacon, priest, and then bishop is understood to hold the fullness of the (ministerial) priesthood, given responsibility by Christ to govern, teach and sanctify the Body of Christ, members of the Faithful. Priests, deacons and lay ministers cooperate and assist their bishop(s) in shepherding a flock.
-- Wikipedia
Legal Definition
An ecclesiastical officer, who is the chief of the clergy of his diocese, and is the archbishop's assistant. Happily for this country, these officers are not recognized by law. They derive all their authority from the churches over which they preside. Bishop's COURT, Eng. law. An ecclesiastical court held in the cathedral of each diocese, the judge of which is the bishop's chancellor.
-- Bouviers Law Dictionary
Legal Definition
In English law. An ecclesiastical dignitary, being the chief of the clergy within his diocese, subject to the archbishop of the province in which his diocese is situated. Most of the bishops are also members of the House of Lords.
-- Black's Law Dictionary
Legal Definition
An officer in charge of a diocese of the Church of England.
-- Ballentine's Law Dictionary