Definition of maniac

< -mania

maniacal >

ma·ni·ac    (mn-k) KEY 

NOUN:

1. An insane person.
2. A person who has an excessive enthusiasm or desire for something: a sports maniac.
3. A person who acts in a wildly irresponsible way: maniacs on the highway.

ADJECTIVE:

Variant of maniacal.

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ETYMOLOGY:
From Late Latin maniacus, maniacal, from Greek maniakos, from mani, madness; see men-¹ in Indo-European roots