conundrum

conundrum

noun

Definition of CONUNDRUM

something hard to understand or explain <the conundrum of how an ancient people were able to build such massive structures without the benefit of today's knowledge and technology>

Synonyms closed book, conundrum, enigma, head-scratcher, mystification, puzzle, puzzlement, riddle, secret

Related Words brainteaser, case, challenge, knot, matter, perplexity, poser, problem, stumper, trouble