specter vs fantasm

specter and fantasm both are nouns.

Word	Noun	Adjective	Verb	Adverb
specter	Yes	No	No	No
fantasm	Yes	No	No	No

As nouns, fantasm is a hypernym of specter; that is, fantasm is a word with a broader meaning than specter:

Other hypernyms of specter include apparition, phantasm, phantasma, phantom, shadow.

As nouns, specter and fantasm are synonyms defined as:

Other synonyms of specter include apparition, phantasm, phantasma, phantom, spectre.

specter (noun)	fantasm (noun)
a mental representation of some haunting experience	something existing in perception only
a ghostly appearing figure	a ghostly appearing figure