lunatic
//ˈluːnətɪk//
Noun
lunaticSingular
lunaticsPlural
1
A person who is mentally ill or behaves in a wildly irrational or reckless manner.
That lunatic was driving on the wrong side of the road.
2
(archaic, offensive) A person suffering from a mental disorder, especially one confined to an asylum.
In the 19th century, lunatics were often confined to asylums.
Adjective
lunaticCanonical form
1
Extremely foolish, eccentric, or absurd; wildly irrational.
His lunatic plan to climb the mountain in winter without proper gear worried everyone.