Source : Webster's Revised Unabridged Dictionary (1913)

Udal \U"dal\, n. & a. Udalborn \U"dal*born`\, Udaler \U"dal*er\,
Udalman \U"dal*man\, etc.
   Vars. of {Odal}, etc. Obs. exc. in Shetland and the Orkney
   Islands, where udal designates land held in fee simple
   without any charter and free of any feudal character.