Sleepwalking is a type of sleep disorder characterized by walking around during sleep.
Common term for sleepwalking; 夢中遊行症 is a rarer, more formal medical synonym.
Compound of 夢中 (むちゅう, 'in a dream') + 遊行 (ゆうこう, 'wandering') + 症 (しょう, 'condition'). The exact historical derivation is uncertain, but the term is a modern medical coinage.