unannounced
adj
without prior warning or notification; unexpected 未事先宣布的; 未通知的; 突如其來(lái)的
make unannounced safety checks on equipment 對(duì)設(shè)備進(jìn)行突然的安全檢查
He arrived unannounced. 他未事先通知而來(lái)到.
??? 情景例句
Mr. Malcolm Stewart, and it looks like a personal letter.