1 (in stories) an imaginary creature that is very large, ugly and frightening:
a monster with three heads * prehistoric monsters
2 an animal or a thing that is very large or ugly:
Their dog's an absolute monster!
3 a person who is very cruel and evil
4 (humorous) a child who behaves badly
adjective [onlybeforenoun] (informal) unusually large:
monster mushrooms
