The Collaborative International Dictionary of English v.0.48:

Rabdomancy \Rab"do*man`cy\ (r[a^]b"d[-o]*m[a^]n`s[y^]), n. [Gr.
   "ra`bdos rod + -mancy.]
   Divination by means of rods or wands. [Written also
   rhabdomancy.] --Sir T. Browne.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rhabdomancy \Rhab"do*man`cy\, n.
   Same as Rabdomancy.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rhabdomancy
    n 1: searching for underground water or minerals by using a
         dowsing rod [syn: dowse, dowsing, rhabdomancy]