Emily Dickinson Lexicon

apparition (-s), n. [Fr. < L. 'appear at a summons', 'wait upon', 'attend'; see appear, v.]

1. Vision; dream; mirage; illusion; phenomena; supposed fantasy; [fig.] epiphany; first appearance of Christ to his disciples after his death and resurrection (see John 20:24-29).
2. Spirit being; angel; other-world personage; visitor from the spirit world.