ma|gis|te|ri|al [ˌmædʒıˈstıəriəl US -ˈstır-] adj
[Date: 1600-1700; : Late Latin; Origin: magisterialis, from Latin magister; MAGISTRATE]
1.) a magisterial way of behaving or speaking shows that you think you have authority
his magisterial voice
2.) a magisterial book is written by someone who has very great knowledge about a subject
his magisterial study of the First World War
3.) [only before noun]
connected with or done by a magistrate
>magisterially adv

Dictionary of contemporary English. 2013.