›something strange or unknown which has not yet been explained or understood: [C]Despite years of study, sleepwalking remains a mystery.[U]The details of the scandal are shrouded in mystery.›A mystery is also a book, movie, or play about a crime or other event that is difficult to explain: [C]a murder mysterymysterious
/mɪˈstɪər·i·əs/adj›He tried to convince this mysterious woman to go out with him.mysteriously
/mɪˈstɪər·i·əs·li/adv›The light mysteriously came on, although no one was near the switch.