fiat

noun

fi·​at ˈfē-ət 

-ˌat, 

-ˌät;

ˈfī-ət, 

-ˌat 

1

: an authoritative or arbitrary order : decree

government by fiat

2

: an authoritative determination : dictate

a fiat of conscience

3

: a command or act of will that creates something without or as if without further effort

According to the Bible, the world was created by fiat.

Synonyms of fiat

• decree
• edict
• ruling
• directive

Examples of fiat in a Sentence

He runs the company by fiat.

the school principal issued a fiat that caps were not to be worn inside the school, and that was that

Recent Examples on the Web

The deference with which that body has bowed to presidential fiat would make Page and William Maclay shudder. —Jake Lundberg, The Atlantic, 7 Jan. 2026

Some of the speedy progress that Los Angeles has seen may be due to regulatory changes imposed by fiat in the aftermath of the fire. —Calmatters, Daily News, 7 Jan. 2026

In that corner of the market, the debasement trade endured — less as a sweeping judgment on fiat, more as a focused bet on rates, policy and protection. —Bloomberg, Mercury News, 29 Dec. 2025

It cannot be bought or declared by fiat; it must be earned through practice. —Zongyuan Zoe Liu, Foreign Affairs, 16 Dec. 2025

Word History

Etymology

Latin, let it be done, 3rd singular present subjunctive of fieri to become, be done — more at be

First Known Use

circa 1631, in the meaning defined at sense 3

Phrases Containing fiat

• fiat money

Kids Definition

fiat

noun

fi·​at ˈfē-ət  -at 

-ät;

ˈfī-ət, 

-at

: an order from someone in charge

Legal Definition

fiat

noun

fi·​at ˈfē-ˌät, -ˌat, -ət; ˈfī-ˌat 

1

: decree

2

: an authoritative but arbitrary order

a brazen act of judicial fiat

—L. H. Tribe