undreamt vs unimagined

undreamt and unimagined both are adjectives.

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

As adjectives, undreamt and unimagined are synonyms defined as:

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

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