狐假虎威 is a classical Chinese idiom (chengyu) that literally means 'the fox borrows the tiger’s might.' It originates from an ancient fable in which a fox, caught by a tiger, tricks the tiger into believing that the gods appointed the fox as ruler of the forest — and to prove it, the fox walks ahead while the tiger follows. All the other animals flee, not from the fox, but from the tiger behind it. Thus, the fox appears powerful only because it's riding on the tiger’s authority.

The idiom describes people who intimidate or boss others around not through their own ability or status, but by exploiting someone else’s power, influence, or position — often a superior, patron, or powerful ally. It carries a strong negative connotation, implying hypocrisy, cowardice, and illegitimate authority. It’s commonly used in commentary, journalism, and everyday speech to criticize those who act arrogantly under borrowed clout.