捣乱 (dǎo luàn) means 'to cause trouble' or 'to make a disturbance' — it emphasizes deliberate, often minor troublemaking (e.g., pranks or meddling). It is more specific than the broader verb 闹 (nào, 'to disturb'), and refers to less serious trouble than 闹事 (nào shì, which implies a public disturbance or riot). 捣乱 is a separable verb: other words can be inserted (e.g., 捣了一次乱).