From Longman Dictionary of Contemporary Englishmegalomaniameg‧a‧lo‧ma‧ni‧a /ˌmeɡələʊˈmeɪniə $ -loʊ-/ noun [uncountable] MICONTROLwhen someone wants to have a lot of power for themselves and enjoys having control over other people’s lives, sometimes as part of a mental illness
Examples from the Corpus
megalomania• From the time of Stalin, at least, modesty and megalomania have gone hand in hand.• Despite their evident megalomania, no coherent vision informed them.• Personally they are petty, self-indulgent and vengeful to a degree that suggests galloping megalomania.• Sometimes charming, he could also be egocentric to the point of megalomania.• The 1890s saw the triumph of megalomania as size took over and passengers and tracks increased in number.• He, too, considers MacArthur's megalomania.Origin megalomania (1800-1900) megalo- “large” (from Greek megas; → MEGA-) + mania 