うちべんけい
someone haughty and boastful at home but meek and reserved outside; being a lion at home and a mouse abroad
Noun
彼かれは内弁慶うちべんけいだ。
He is a lion at home and a mouse outside.
内弁慶うちべんけいは誰だれでもできる。
Every cock crows on his own dunghill.