'Yán dǎ' (literally 'strict strike') is a fixed noun phrase meaning 'crack down (on crime)'—a government-led, intensive law enforcement campaign targeting specific criminal activities such as drug trafficking, organized crime, or corruption. The character 严 (yán) conveys strictness, severity, and zero tolerance, while 打 (dǎ) here functions idiomatically as 'to strike' or 'to suppress', not its literal sense of 'hit'. Together, they form a bureaucratic and media term widely used in official announcements, news reports, and policy documents.

This term carries strong institutional and political connotations; it's rarely used in casual speech or personal contexts. It almost always appears with prepositions like '对...进行严打' ('carry out a crackdown on...') or as the object of verbs like '开展' ('launch') or '加强' ('strengthen'). Historically, major 'yán dǎ' campaigns were launched in the 1980s, 1990s, and 2000s, often timed to address surges in public concern over safety or social order.