Source : Webster's Revised Unabridged Dictionary (1913)

Fiat \Fi"at\, n. [L., let it be done, 3d pers. sing., subj.
   pres., fr. fieri, used as pass. of facere to make. Cf. {Be}.]
   1. An authoritative command or order to do something; an
      effectual decree.

            His fiat laid the corner stone.       --Willis.

   2. (Eng. Law)
      (a) A warrant of a judge for certain processes.
      (b) An authority for certain proceedings given by the Lord
          Chancellor's signature.

   {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.

Source : WordNet®

fiat
     n : a legally binding command or decision entered on the court
         record (as if issued by a court or judge); "a friend in
         New Mexico said that the order caused no trouble out
         there" [syn: {decree}, {edict}, {order}, {rescript}]