megalomaniac /ˌmɛɡəloʊˈmeɪniæk/adjective 1noun 1forms 3 adjective1 •Of, exhibiting, or affected with megalomania.Often, for good measure, Hitler is given as an example of a megalomaniac person. So, for our convenience, Hitler personifies the illness called megalomania[…] — 2013 noun1 •One affected with or exhibiting megalomania.'Well, I don't know him well enough yet to say, but I will admit that if he is not a mere bullying megalomaniac, and if what he says is true, then he certainly is in a class by himself.' — 1929 formsmegalomaniacs · more megalomaniac · most megalomaniac