occultation

noun3

1. •
   The state of being occult (“hidden, undetected”).
2. •
   An astronomical event that occurs when one celestial object is hidden by another celestial object that passes between it and the observer when the nearer object appears larger and completely hides the more distant object.
3. •
   The disappearance of the Twelfth Imam, or Mahdi, who is believed alive and present in this world, but hidden until his reappearance at the end of time.