Webster's Dictionary 
(1): ( n.) Of or pertaining to an office or public trust; as, official duties, or routine.
(2): ( a.) An ecclesiastical judge appointed by a bishop, chapter, archdeacon, etc., with charge of the spiritual jurisdiction.
(3): ( n.) Derived from the proper office or officer, or from the proper authority; made or communicated by virtue of authority; as, an official statement or report.
(4): ( n.) Approved by authority; sanctioned by the pharmacopoeia; appointed to be used in medicine; as, an official drug or preparation. Cf. Officinal.
(5): ( n.) Discharging an office or function.
(6): ( a.) One who holds an office; esp., a subordinate executive officer or attendant.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
is the title given to an episcopal ecclesiastic who is entrusted with the trial of offenses in a diocese. The official originated in the 12th century. as if to check the power of the archdeacon. The official of an archdeacon stands to him as a chancellor to a bishop. But there was a practice in very early times in the Church which gave rise to such appointment. The bishops, as far back as the days of St. Gregory and St. Basil, employed assistants; and pope Damasus sent the priest Simplicius to assist St. Ambrose. The Council of Lateran contented itself with suggesting the employment of "fitting men" to assist bishops; and it appears that at first the titles of vicar- general and official were tenable together, as now in Italy, for the administration by one person both of voluntary and contentious jurisdiction. A bishop, when absent from his diocese, or when ill or incapable, was obliged to appoint a vicar. He was sometimes called a "missus dominicus." The principal officials and vicar-general in temporals and spirituals hold the consistory court as the bishop's representatives as if he sat in person. The official has a territory or district, and holds his' office by commission, for hearing causes in a whole diocese, but without the power of inquiry, correction, or punishment of offenses; he can only deprive of a benefice, or give admission to it by special commission. A vicar-general holds all these powers except collation to a benefice. A commissary-general is a special deputy. An official's powers terminate with the death of him by whose appointment he acts, and he may also be recalled. An appeal lies from his sentence, not to the bishop, but to him to whom an appeal would be made from the bishop himself. The official principal resides in the chief place, and is an ordinary; others are deputies, "officiales foranei" (i.e. living out of it), and from them appeal lies to the bishop. The official principal is the assistant of the bishop in matters of a civil or criminal nature, to aid him in points of law and to defend the rights of the Church. These officers were not at first deputed and assigned to any certain place, but supplied the office of the bishops at' large in hearing ecclesiastical causes which were of a contentious jurisdiction. They were called "judices," or "officiales foranei," viz. "officiales astricti cuidam foro dioceseos tantum." To them. the cognizance of causes is generally committed by such as have ecclesiastical jurisdiction throughout all the diocese, but not the power of inquisition, nor the correction of crimes, nor can they remove persons from the benefices or collate to benefices without a special commission. The archdeacon's official exercises jurisdiction in certain parts of a diocese for cognizance and hearing of causes transferred, in virtue of the office itself, by some general commission made to him for that purpose, and he may visit in the right of the archdeacon when the latter himself is hindered.