to violate or go against laws, regulations, or prohibitions

the whole world; all of society; everywhere on earth

Connects a describing word or phrase to the noun it describes, similar to 的 de but used in formal or literary writing.

(literary) a fault or error; a wrongdoing; used almost exclusively in the idiom 冒天下之大不韪 mào​tiān​xià​zhī​dà​bù​wěi