1mon·ster 
/ˈmɑ:nstɚ/ noun
plural mon·sters /ˈmɑ:nstɚ/ noun [count] 1 : a strange or horrible imaginary creature
▪ mythical monsters ▪ a sea monster ▪ a monster movie [=a movie about monsters] 2 informal : something that is extremely or unusually large
▪ That car is a monster. ▪ It's a monster of a house. [=a very large house] 3 : a powerful person or thing that cannot be controlled and that causes many problems
▪ Inflation has become an economic monster. 4 a : an extremely cruel or evil person
▪ His father was a monster who punished his children for no reason. ▪ You don't want to work for that monster.
b : a person (such as a child) who behaves very badly
▪ My nephew is a little monster.
▪ mythical monsters ▪ a sea monster ▪ a monster movie [=a movie about monsters]
▪ That car is a monster. ▪ It's a monster of a house. [=a very large house]
▪ Inflation has become an economic monster.
▪ His father was a monster who punished his children for no reason. ▪ You don't want to work for that monster.
b : a person (such as a child) who behaves very badly
▪ My nephew is a little monster.
— see also green-eyed monster
