From WordNet (r) 2.0 (August 2003) [wn]:
phantasma
n 1: a ghostly appearing figure; "we were unprepared for the
apparition that confronted us" [syn: apparition,
phantom, phantasm, specter, spectre]
2: something existing in perception only; "a ghostly apparition
at midnight" [syn: apparition, phantom, phantasm,
shadow]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Phantasma \Phan"tas"ma\, n. [L.]
A phantasm.
[1913 Webster]