Hadrian Syllabification: (Ha·dri·an)Pronunciation: /ˈhādrēən/Definition of Hadrian ( ad 76-138), Roman emperor 117–138; full name Publius Aelius Hadrianus. The adopted successor of Trajan, he toured the provinces of the empire and secured the frontiers. Hadrian in other Oxford dictionaries Definition of Hadrian in the British & World English dictionary