ma ‧ ni ‧ ac /ˈmeɪniæk/ BrE AmE noun [countable]
[ Date: 1500-1600 ; Language: Late Latin ; Origin: maniacus , from Greek maniakos , from mania ; ⇨ ↑ mania ]
1 . informal someone who behaves in a stupid or dangerous way SYN lunatic :
He drove like a maniac to the hospital.
Suddenly this maniac ran out into the middle of the road.
2 . religious/sex maniac informal someone who you think is too involved or interested in religion or sex SYN freak :
The woman’s a sex maniac if you ask me.
3 . someone who is mentally ill
homicidal maniac (=someone who kills people)