1) The condition of speaking the
truth and having no one believe you.
2) The condition of being
able to predict the future, be it the outcome of a particular event, or the reactions of others to the same event, and having no one believe your prophecy until it transpires.
3) Being able to see or understand things
long before others, often resulting in them coming to the same conclusions
long after your own initial analysis.
(All definitions come from Cassandra, the queen in Greek mythology who was appointed by Apollo with an inability to
lie, yet cursed by having no one believe her prophecies.)