The Collaborative International Dictionary of English v.0.48:

Domesday \Domes"day`\, n.
   A day of judgment. See Doomsday. [Obs.]
   [1913 Webster]

   Domesday Book, the ancient record of the survey of most of
      the lands of England, made by order of William the
      Conqueror, about 1086. It consists of two volumes, a large
      folio and a quarto, and gives the proprietors' tenures,
      arable land, woodland, etc. [Written also Doomsday
      Book.]
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

DOMESDAY, or DOMESDAY-BOOK. An ancient record made in the time of William
the Conqueror, and now remaining in the English exchequer, consisting of two
volumes of unequal sizes, containing surveys of the lands in England.