unannounced
🇺🇸
/ˌʌnəˈnaʊnst/
🇬🇧
/ˌʌnəˈnaʊnst/
Not previously mentioned or expected; arriving or occurring without warning.
The teacher made an unannounced visit to our class to check our progress.
선생님이 우리 반에 예고 없이 방문하여 우리의 진도를 확인했습니다.