The Collaborative International Dictionary of English v.0.48:

Stillbirth \Still"birth`\, n.
   1. The birth of a dead fetus.
      [1913 Webster]

   2. a fetus which was born dead.
      [PJC]

WordNet (r) 3.0 (2006):

stillbirth
    n 1: a natural loss of the products of conception [syn:
         spontaneous abortion, miscarriage, stillbirth] [ant:
         live birth]