Ca·lig·u·la (kə-lĭg'yə-lə) Emperor of Rome (37-41) who succeeded his adoptive father, Tiberius. After a severe illness, he displayed the ruthlessness, extravagance, and megalomania that led to his assassination.
A cruel and insane ruler of the Roman Empire in the first century a.d.; one of the twelve Caesars. To humiliate the senators of Rome, he appointed his horse to the senate.