The Collaborative International Dictionary of English v.0.48:

Dependant \De*pend"ant\, Dependance \De*pend"ance\, n.,
Dependancy \De*pend"an*cy\, n.
   See Dependent, Dependence, Dependency.
   [1913 Webster]

   Note: The forms dependant, dependance, dependancy are from
         the French; the forms dependent, etc., are from the
         Latin. Some authorities give preference to the form
         dependant when the word is a noun, thus distinguishing
         it from the adjective, usually written dependent.
         [1913 Webster]

WordNet (r) 3.0 (2006):

dependant
    adj 1: contingent on something else [syn: dependent,
           dependant, qualified]
    2: addicted to a drug [syn: dependent, dependant, drug-
       addicted, hooked, strung-out]
    n 1: a person who relies on another person for support
         (especially financial support) [syn: dependant,
         dependent]