undreamed vs unimagined

undreamed and unimagined both are adjectives.

Word	Noun	Adjective	Verb	Adverb
undreamed	No	Yes	No	No
unimagined	No	Yes	No	No

As adjectives, undreamed and unimagined are synonyms defined as:

Other synonyms of undreamed include undreamed of, undreamt, undreamt of.

undreamed (adjective)	unimagined (adjective)
not imagined even in a dream	not imagined even in a dream