What is Archdeacon?

Legal Definition
An archdeacon is a senior clergy position in the Syriac Orthodox Church, Church of the East, Chaldean Catholic Church, Anglican Communion, St Thomas Christians, Eastern Orthodox churches and some other Christian denominations, above that of most clergy and below a bishop. In the High Middle Ages it was the most senior diocesan position below a bishop in the Roman Catholic Church. An archdeacon is often responsible for administration within an archdeaconry, which is the principal subdivision of the diocese. The Oxford Dictionary of the Christian Church has defined an archdeacon as "A cleric having a defined administrative authority delegated to him by the bishop in the whole or part of the diocese." The office has often been described metaphorically as that of oculus episcopi, the "bishop's eye".
-- Wikipedia
Legal Definition
A dignitary of the Anglican church who has ecclesiastical jurisdiction immediately subordinate to that of the bishop, either throughout the whoie of his diocese or in some particular part of it.
-- Black's Law Dictionary
Legal Definition
An ecclesiastical officer subordinate to a bishop.
-- Ballentine's Law Dictionary