사문화가 · 사문화를 (사문화되다)
becoming a dead letter, falling into disuse (of a law)
Example
그 법은 오래전에 사실상 사문화되었어요.
That law effectively became a dead letter long ago.
Word parts
사 dead+문 writing+화 -ize
Literally 'becoming dead writing': a law that exists on paper but is never enforced.
Good to know
Mostly used as 사문화되다; it is the exact counterpart of the English idiom 'dead letter'.