The Collaborative International Dictionary of English v.0.48:

Beldam \Bel"dam\ Beldame \Bel"dame\, n. [Pref. bel-, denoting
   relationship + dame mother: cf. F. belledame fair lady, It.
   belladonna. See Belle, and Dame.]
   [1913 Webster]
   1. Grandmother; -- corresponding to belsire.
      [1913 Webster]

            To show the beldam daughters of her daughter.
                                                  --Shak.
      [1913 Webster]

   2. An old woman in general; especially, an ugly old woman; a
      hag.

   Syn: hag, beldam, witch, crone.
        [1913 Webster]

              Around the beldam all erect they hang. --Akenside.
        [1913 Webster]

WordNet (r) 3.0 (2006):

beldame
    n 1: an ugly evil-looking old woman [syn: hag, beldam,
         beldame, witch, crone]
    2: a woman of advanced age [syn: beldam, beldame]