ignis fatuus vs jack-o'-lantern

ignis fatuus and jack-o'-lantern both are nouns.

Word	Noun	Adjective	Verb	Adverb
ignis fatuus	Yes	No	No	No
jack-o'-lantern	Yes	No	No	No

As nouns, ignis fatuus and jack-o'-lantern are synonyms defined as:

ignis fatuus and jack-o'-lantern: a pale light sometimes seen at night over marshy ground

Other synonyms of ignis fatuus include friar's lantern, will-o'-the-wisp.

ignis fatuus (noun)	jack-o'-lantern (noun)
an illusion that misleads	lantern carved from a pumpkin
a pale light sometimes seen at night over marshy ground	a pale light sometimes seen at night over marshy ground