A riddle, puzzle, or an enigma; something mysterious or unexplained.
子供たちはなぞなぞを出し合って遊んだ。
The children played by giving each other riddles.
事件の真相はまだ謎のままだ。
The truth behind the incident remains a mystery.
この機械が動かない原因は謎だ。
The reason this machine won't work is a mystery.
Describing something enigmatic or mysterious; often used in the form '謎の〜' (mysterious ~).
謎の人物が夜中に屋敷を訪れたという。
It is said that a mysterious person visited the mansion at night.
古い日記には謎の記号が書かれていた。
The old diary had mysterious symbols written in it.
彼の言動は周囲には謎のままだった。
His behavior remained a mystery to those around him.