‘振聋发聩’ literally means ‘to shake the deaf and rouse the hard-of-hearing,’ but it’s used figuratively to describe words, ideas, or actions that are so powerful and insightful that they awaken people who are ignorant, indifferent, or mentally ‘deaf’ to important truths. Each character contributes: 振 (to shake/stir), 聋 (deafness, symbolizing ignorance), 发 (to awaken/activate), and 聋 (deafness) + 聩 (a classical term for profound deafness or mental dullness). Together, they evoke a vivid image of breaking through deep-seated apathy or misunderstanding.

This idiom is formal and literary, often found in speeches, editorials, academic writing, or serious commentary—never in casual conversation. It carries strong positive connotations of moral urgency and intellectual clarity, and is frequently applied to critiques of social injustice, scientific breakthroughs, or philosophical revelations that challenge prevailing assumptions.