He hurled himself around Oprah Winfrey's set like a maniac declaring his love for Katie Holmes.
The maniac suspects then killed another person in a Walmart, and then themselves.
There's a maniac who rents Yankee Stadium, not knowing how to fill the seats.
c.1600, "pertaining to mania; insane," from French maniaque (14c.), from Late Latin maniacus, from Greek maniakos, from mania (see mania). Borrowed at first in French form; Latinized in English from 1727. The noun is attested from 1763, from the adjective.
maniac ma·ni·ac (mā'nē-āk')
An insane person.