unannounced
adj. B2 Upper Intermediate US //ˌənəˈnaʊnst// UK //ʌnɐnˈaʊnst// unan·nounced
adj. happening without any warning or notice. You use this to describe someone arriving or something starting when you did not expect it.
adj. occurring or arriving without prior notice or warning. Often used to describe visits, inspections, or changes that happen suddenly.
The manager made an unannounced visit to the office.
The health inspector arrived unannounced to ensure the kitchen staff followed safety rules every day.
The sudden, unannounced departure of the CEO caused a sharp drop in the company's stock price as investors scrambled to understand the leadership vacuum.
Usage
Typically used attributively before a noun, but can also follow linking verbs like 'remain' or 'be'.