The Collaborative International Dictionary of English v.0.48:

Bedpan \Bed"pan`\, n.
   1. A pan for warming beds. --Nares.
      [1913 Webster]

   2. A shallow chamber vessel, so constructed that it can be
      used by a sick person in bed.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bedpan
    n 1: a shallow vessel used by a bedridden patient for defecation
         and urination

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "bedpan":
   can, chamber, chamber pot, chemical closet, chemical toilet,
   commode, crapper, jerry, john, johnny, jordan, latrine, piss pot,
   potty, potty-chair, stool, throne, thunder mug, toilet, urinal,
   water closet