The Collaborative International Dictionary of English v.0.48:

Deathbed \Death"bed\, n.
   The bed in which a person dies; hence, the closing hours of
   life of one who dies by sickness or the like; the last
   sickness.
   [1913 Webster]

         That often-quoted passage from Lord Hervey in which the
         Queen's deathbed is described.           --Thackeray.
   [1913 Webster]

WordNet (r) 3.0 (2006):

deathbed
    n 1: the last few hours before death
    2: the bed on which a person dies