大おおきな顔かおをする

expression, suru verb (irregular)

act important; swagger; put on airs

Idiomatic expression describing someone who behaves as if they are more important or influential than they really are, often with a negative or mocking tone.

• 彼かれは新しん入いりなのに、もう大おおきな顔かおをしている。

  Even though he's a newcomer, he's already acting like he's important.