1 [count] : something that is not known
▪ Where they went is a mystery. [=no one knows where they went] ▪ The girl's name remains a mystery. : something that is difficult to understand or explain ▪ The mystery surrounding/of her disappearance has never been solved. ▪ His success is something of a mystery. = His success is a bit of a mystery. ▪ The cause of the disease remains a mystery to scientists. ▪ I don't know how he did it. It's a mystery to me! 2 [noncount] : the quality of being difficult to understand or explain : the quality of being mysterious
▪ The experiment is cloaked/shrouded/veiled in mystery. ▪ There is an air of mystery surrounding her. = She is a woman of mystery. ▪ There's no mystery (to/as to/about) why we're here. = It's no mystery why we're here. [=we know why we are here] 3 [count] : a religious event or idea that cannot be fully understood or explained
▪ the mystery of creation 4 [count] : a book, play, or movie that describes a crime and the process of solving it
▪ She has written many adventure novels and murder mysteries. — often used before another noun ▪ mystery novels/stories ▪ She's a mystery writer. 5 [count] : someone or something whose identity has been kept secret especially in order to create interest or excitement — usually used before another noun ▪ We'll reveal the identity of today's mystery guest after these commercials. ▪ You'll find a mystery prize in each box.