紊乱 (wěnluàn) is a formal, written word for something that is disordered or chaotic, especially a system, order, or mental state that has become irregular or disrupted. It is more formal and specific than the common HSK4 word 乱 (luàn), and often implies a breakdown of normal functioning (e.g., endocrine or traffic disorder) rather than general messiness. 混乱 (hùnluàn) is close but broader; 紊乱 typically suggests a system's internal order is disturbed.