Definition of apparitions:
(n) :
An unexpected, wonderful, or preternatural appearance; especially, one by a ghost, phantom, or suchlike; the entity itself.
(n) :
An act of becoming visible; appearance; visibility.
(n) :
The thing appearing; a visible object; a form.
(n) :
(astronomy) The first appearance of a star or other luminary after having been invisible or obscured; opposed to occultation.
(n) :
(astronomy) A period of consecutive days or nights when a particular celestial body may be observed, beginning with the heliacal rising of the body and ending with its heliacal setting.