All 3 Uses

apparition
in
All Quiet on the Western Front
(Edited)

They are soundless apparitions that speak to me, with looks and gestures silently, without any word—
p. 120.7 *

apparitions = ghostlike figures
They arise no more; we are dead and they stand remote on the horizon, they are a mysterious reflection, an apparition, that haunts us, that we fear and love without hope.
p. 121.9

apparition = ghostlike figure
And at night, waking out of a dream, overwhelmed and bewitched by the crowding apparitions, a man perceives with alarm how slight is the support, how thin the boundary that divides him from the darkness.
p. 274.9

apparitions = ghostlike figures

Definitions:

(1) (apparition as in: a headless apparition)
a ghostlike figure or its appearance
(2) (meaning too rare to warrant focus)
More rarely, apparition can refer to any strange, other-worldly, thing or its appearance. Even more rarely, apparition can by a synonym for appearance. The Harry Potter series uses the word both ways.