A very nuanced Latin word that is difficult to translate; (very) roughly it means authority.
In Ancient Rome, a man's auctoritas measured his pre-eminence in society, his clout, his public importance and most of all his ability to influence events through public office.
All Roman magistracies conferred auctoritas as an intrinsic part of their nature. Some religious offices, such as the Pontifex Maximus, and Senatorial positions, such as the Princeps Senatus conferred auctoritas. Additionally, priests, augurs, consulars, and even private individuals outside Senate ranks could own auctoritas.