unannounced

adj. no anunciado, no avisado, no notificado, sin ser anunciado

sin ser anunciado

Ex: The arrival of the school doctor or dentist or of well-knwon personalities visiting the school normally occur unannounced.

(adj.) = inesperado, imprevisto, sin previo aviso, sin avisar, sin ser anunciado de antemano
Ex: The arrival of the school doctor or dentist or of well-knwon personalities visiting the school normally occur unannounced.