phantasm
Concise Oxford English Dictionary © 2008 Oxford University Press:
phantasm /ˈfantaz(ə)m/
▶noun literary an illusion or apparition.
– derivatives
phantasmal adjective,
phantasmic adjective.
phantasmal adjective,
phantasmic adjective.
– origin ME: from OFr. fantasme, via L. from Gk phantasma, from phantazein ‘make visible’, from phainein ‘to show’.
'phantasm' also found in these Oxford entries:

