apparition

plural apparitions

1. An act of becoming visible; appearance; visibility.

   the sudden apparition of the Spaniards

   1855–1858, William H[ickling] Prescott, History of the Reign of Philip the Second, King of Spain, volume (please specify |volume=I to III), Boston, Mass.: Phillips, Sampson, and Company, →OCLC

   1 more example

   The apparition of Lawyer Clippurse occasioned much speculation in that portion of the world.

   1814 July 7, [Walter Scott], Waverley; or, ’Tis Sixty Years Since. […], volume (please specify |volume=I to III), Edinburgh: […] James Ballantyne and Co. for Archibald Constable and Co.; London: Longman, Hurst, Rees, Orme, and Brown, →OCLC

2. The thing appearing; a visible object; a form.

   […] which apparition, it seems, was you.

   1709 August 26 (Gregorian calendar), Isaac Bickerstaff [et al., pseudonyms; Richard Steele et al.], “Monday, August 16, 1709”, in The Tatler, number 55; republished in [Richard Steele], editor, The Tatler, […], London stereotype edition, volume I, London: I. Walker and Co.; […], 1822, →OCLC

3. An unexpected, wonderful, or preternatural appearance; especially, one by a ghost, phantom, or suchlike; the entity itself.

   The region's economy is buoyed by tourism driven by past apparitions of the Virgin Mary.

   5 more examples

   The attic is said to be haunted by the ghostly apparition of a young girl who died there.

   He spoke to the apparition, and although its lips did not move, he somehow heard its reply.

   I think it is the weakness of mine eyes / That shapes this monstrous apparition.

   1599 (first performance), William Shakespeare, “The Tragedie of Iulius Cæsar”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, [Act IV, scene iii]

   The heavenly bands […] a glorious apparition.

   1667, John Milton, “Book X”, in Paradise Lost. […], London: […] [Samuel Simmons], and are to be sold by Peter Parker […]; [a]nd by Robert Boulter […]; [a]nd Matthias Walker, […], →OCLC; republished as Paradise Lost in Ten Books: […], London: Basil Montagu Pickering […], 1873, →OCLC

   The apparition wobbled in front of Arthur's eyes, though the truth of the matter is probably that Arthur's eyes were wobbling in front of the apparition.

   1982, Douglas Adams, Life, the Universe and Everything, page 24

   Synonyms: vision

4. astronomyThe first appearance of a star or other luminary after having been invisible or obscured; opposed to occultation.
5. astronomyA 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.