Source : Webster's Revised Unabridged Dictionary (1913)

Formedon \For"me*don\, n. [OF., fr. Latin. So called because the
   plaintiff claimed ``by the form of the gift,: L. per formam
   doni.] (O. Eng. Law)
   A writ of right for a tenant in tail in case of a
   discontinuance of the estate tail. This writ has been
   abolished.