an authoritative decree, sanction, or order

a royal fiat.

a formula containing the word fiat, by which a person in authority gives sanction.

an arbitrary decree or pronouncement, esp. by a person or group of persons having absolute authority to enforce it

The king ruled by fiat.

noun

question , request

noun

authorization , command , decree , dictate , dictum , edict , endorsement , mandate , ordinance , permission , precept , sanction , ukase , warrant , announcement , order , proclamation , rule , writ