megalomania
Concise Oxford English Dictionary © 2008 Oxford University Press:
megalomania/meɡələˈmeɪniə/
▶noun obsession with the exercise of power.
■ delusion about one's own power or importance (typically as a symptom of manic or paranoid disorder).
– derivatives
megalomaniac noun & adjective,
megalomaniacal adjective,
megalomanic adjective.
megalomaniac noun & adjective,
megalomaniacal adjective,
megalomanic adjective.
'megalomania' also found in these Oxford entries:
