Charles Buck Theological Dictionary 
The chief church of a diocese; a church wherein is a bishop's see. The word comes from "chair;" the name seems to have taken its rise from the manner of sitting in the ancient churches of assemblies of private Christians. In these the council, 1:e. the elders and priests, were called Presbyterium; at their head was the bishop, who held the place of chairman, Cathedralis or Cathedraticus; and the presbyters, who sat on either side, also called by the ancient fathers Assessores Episcoporum. The episcopal authority did not reside in the bishop alone, but in all the presbytery, whereof the bishop was president. A cathedral, therefore, originally was different from what it is now; the Christians, till the time of Constantine, having no liberty to build any temple. By their churches they only meant assemblies; and by cathedrals, nothing more than consistories.
Webster's Dictionary 
(1): (a.) Emanating from the chair of office, as of a pope or bishop; official; authoritative.
(2): (n.) The principal church in a diocese, so called because in it the bishop has his official chair (Cathedra) or throne.
(3): (a.) Pertaining to the head church of a diocese; as, a cathedral church; cathedral service.
(4): (a.) Resembling the aisles of a cathedral; as, cathedral walks.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
Bibliography Information McClintock, John. Strong, James. Entry for 'Cathedral'. Cyclopedia of Biblical, Theological and Ecclesiastical Literature. https://www.studylight.org/encyclopedias/eng/tce/c/cathedral.html. Harper & Brothers. New York. 1870.
The Nuttall Encyclopedia 
The principal church in a diocese, and which contains the throne of the bishop as his seat of authority; is of a rank corresponding to the dignity of the bishop; the governing body consists of the dean and chapter.