阻止 (zǔzhǐ) means to stop or prevent something by taking direct action, often to halt something already in progress. It contrasts with 防止 (fángzhǐ), which focuses on preventive measures before something happens, and with 阻碍 (zǔ'ài) / 阻挡 (zǔdǎng), which emphasize obstructing movement or progress rather than stopping an event.