mystery

I UK [ˈmɪst(ə)rɪ] / US noun
Word forms "mystery":
singular mystery plural mysteries
**

1) [countable] something that you are not able to understand, explain, or get information about

I just can't think who she could have been – it's a mystery.

The exact origin of the universe remains a mystery.

solve/unravel a mystery (= explain it):

The police are trying to unravel the mystery of his disappearance.

be a mystery to someone:

Why she left is still a mystery to him.

2)

a) [uncountable] a quality that makes someone or something difficult to explain, understand, or get information about, especially when it also makes them seem interesting or exciting

air/aura of mystery:

a woman with an air of mystery about her

shrouded/cloaked in mystery:

His past is shrouded in mystery.

b) [countable] someone or something that is interesting or exciting because they are difficult to explain, understand, or get information about

David's always been a bit of a mystery.

3) [countable] a story, film, or play in which events take place that are not explained until the end, especially a crime such as murder

an Ellery Queen mystery

4) mysteries

[plural] often humorous information about a subject or activity that only some people are allowed to know mystery of:

You'll learn all about the mysteries of the darkroom and printing processes.

5) [countable] something relating to religion or God that you cannot explain using reason or science but that you believe is true

the mystery of salvation

II UK [ˈmɪst(ə)rɪ] / US adjective [only before noun]

a mystery person or thing is someone or something that you do not know the name of or do not know anything about

a mystery caller