Proper noun

1. Daughter of King Priam of Troy and his queen Hecuba, who captured the eye of Apollo and was granted the ability to see the future. However, she was destined to never be believed.
2. .
   • 1605 William Camden, Remains Concerning Britain, John Russell Smith, 1870, page 56

     But succeeding ages (little regarding S. Chrysosthome's admonition to the contrary) have recalled prophane names, so as now Diana, Cassandra, Hyppolytus, Venus, Lais, names of unhappy disaster are as rife, as ever they were in paganism.

3. A person who makes predictions which are never believed but turn out to be true.