The Collaborative International Dictionary of English v.0.48:

Godchild \God"child`\, n.
   One for whom a person becomes sponsor at baptism, and whom he
   promises to see educated as a Christian; a godson or
   goddaughter. See Godfather.
   [1913 Webster] goddamn
   goddam

WordNet (r) 3.0 (2006):

godchild
    n 1: an infant who is sponsored by an adult (the godparent) at
         baptism