bow-shaped (adjective) crescent: sickle-shaped
Sinonime: Gordian knot,
bewilderment, cliffhanger,
conundrum,
crux, cryptogram, grabber,
knot*, mind-boggler, mind-twister, mystification,
parable, perplexity,
problem,
puzzle, puzzlement, puzzler,
question, question mark,
riddle,
secret, sixty-four dollar question, sphinx, sticker, stickler, stumper, teaser, tough nut to crack, twister,
why*