unexplained
adj. 未解释的；原因不明的；莫名其妙的
例句
He died in unexplained circumstances.
他死因不明。
《牛津词典》
An unexplained death is difficult to come to terms with.
原因不明的死亡是难以接受的。
《柯林斯英汉双解大词典》
The city's water supply has been cut for unexplained reasons.
城市的供水被莫名其妙地切断了。
