物もの知しらず

noun, noun which may take the genitive case particle 'no'

ignorance; stupidity; ignorant person; stupid person

Refers to a lack of knowledge or common sense, often used critically or self-deprecatingly. Can describe a person or the quality itself.

• あんなことを言いうなんて、彼かれはまったくの物もの知しらずだ。

  Saying something like that, he is completely ignorant.

• 物もの知しらずで恥はじをかいた。

  I embarrassed myself because of my ignorance.