a fox borrowing the tiger's authority; someone who acts arrogantly on borrowed authority
Idiomatic expression derived from a Chinese fable. Used to describe a person who bullies others by relying on someone else's power or influence. The literal meaning is 'a fox that borrows the authority of a tiger'.
He acts arrogantly under his boss's authority. He's exactly a fox borrowing the tiger's authority.
An attitude like a fox borrowing the tiger's authority only invites resentment from those around you.