Augustus

The honorific given to the supreme head or emperor of the Roman Empire. The term, which simply means 'the venerable' or 'the majestic,' was first used of Octavian when—fearful of offending as well losing the leadership of the man who had defeated Mark Antony and Cleopatra, returned to Rome, and renounced the power first granted him to fight Mark Antony—the Roman Senate rewarded him with the honour.

In subsequent periods of Roman history, and especially during the reign of Diocletian when he reformed the administration so that there was two emperors and two deputy emperors, the senior emperors were called Augusti and the deputies Caesares (a model called the Tetrarchy (2)).