Definition of Fiat

(Lat. "Let it be done.”) In old English practice, a short order or warrant of a judge or magistrate directing some act to be done; an authority issuing from some competent source for the doing of some legal act.

One of the proceedings in the English bankruptcy practice, being a power, signed by the lord chancellor, addressed to the court of bankruptcy, authorizing the petitioning creditor to prosecute his complaint before it. By the statute 12 & 13 Viet., c. 116, fiats were abolished.

Arbitrary or authoritative order or decision.

Joint fiat. In old English law, a fiat in bankruptcy, issued against two or more trading partners.

That's the definition of Fiat in Black's Law Dictionary 6th Edition. Courtesy of