/ ˈluːnətɪk; NAmE / noun , adjective
■ noun
1.
a person who does crazy things that are often dangerous
SYN maniac :
This lunatic in a white van pulled out right in front of me!
2.
( old-fashioned ) a person who is severely mentally ill (the use of this word is now offensive)
■ adjective
crazy, ridiculous or extremely stupid :
lunatic ideas
a lunatic smile
•
IDIOMS
- the lunatic fringe
••
WORD ORIGIN
Originally from the Latin lunaticus ( luna = moon), because people believed that the changes in the moon made people go mad temporarily.