D defs.my
Entry 2 senses Webster, 1913

Fiat

/fī'-ăt/ · Fi·at · IPA /ˈfaɪæt/
01 n. An authoritative command or order to do something; an effectual decree.
  1. 1.
    An authoritative command or order to do something; an effectual decree.
    “His fiat laid the corner stone.” — Willis.
  2. 2.
    A warrant of a judge for certain processes.(Eng. Law)
Phrases & compounds
Fiat money — irredeemable paper currency, not resting on a specie basis, but deriving its purchasing power from the declaratory fiat of the government issuing it.