kaiju
Kaiju (怪獣) is a Japanese word that means "strange beast," but often translated in English as "monster." Specifically, it is used to refer to a genre of tokusatsu entertainment involving giant monsters.
Related terms include kaiju eiga (怪獣映画, monster movie), a film featuring kaiju, kaijin (怪人, humanoid monsters) and daikaiju (大怪獣, giant monster), specifically meaning the larger variety of monsters.
The most famous kaiju is Godzilla. Other well-known kaiju include Mothra, Anguirus, Rodan, Gamera, and King Ghidorah.