1 (informal) a person who behaves in an extremely dangerous, wild, or stupid way:
He was driving like a maniac.
2 a person who has an extremely strong desire or enthusiasm for sth, to an extent that other people think is not normal:
a football / religious / sex maniac
3 (psychology) a person suffering from mania:
a homicidal maniac
maniac adjective [onlybeforenoun]:
a maniac driver / fan / killer
