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]

WordNet (r) 3.0 (2006):

Domesday Book
    n 1: record of a British census and land survey in 1085-1086
         ordered by William the Conqueror [syn: Domesday Book,
         Doomsday Book]