An expression criticizing someone who shamelessly acts as if they have done nothing wrong; brazen and impudent despite being at fault.
人の物を盗んでおきながら、盗人猛々しい態度で平然としていた。
He stole someone's belongings and yet acted brazenly as if nothing had happened.
あの店は不良品を売っておきながら交換もせず、盗人猛々しいと苦情が相次いだ。
That shop sold defective goods and refused exchanges; complaints said it was shameless.
盗人猛々しいとは、やましい心があるのに平気でいる人を非難する言葉だ。
'盗人猛々しい' is a word used to criticize someone who is unashamed despite having a guilty conscience.