pipe dream vs phantasy

pipe dream and phantasy both are nouns.

Word	Noun	Adjective	Verb	Adverb
pipe dream	Yes	No	No	No
phantasy	Yes	No	No	No

As nouns, phantasy is a hypernym of pipe dream; that is, phantasy is a word with a broader meaning than pipe dream:

pipe dream: a fantastic but vain hope (from fantasies induced by the opium pipe)
phantasy: imagination unrestricted by reality

Other hypernyms of pipe dream include fantasy.

pipe dream (noun)	phantasy (noun)
a fantastic but vain hope (from fantasies induced by the opium pipe)	imagination unrestricted by reality
	something many people believe that is false
	fiction with a large amount of imagination in it