brain-teaser vs enigma

brain-teaser and enigma both are nouns.

Word	Noun	Adjective	Verb	Adverb
brain-teaser	Yes	No	No	No
enigma	Yes	No	No	No

As nouns, brain-teaser and enigma are synonyms defined as:

Other synonyms of brain-teaser include conundrum, riddle.

brain-teaser (noun)	enigma (noun)
a difficult problem	something that baffles understanding and cannot be explained
	a difficult problem