공식적으로 발표되거나 대중에게 알려지지 않은
Not made known to the public or officially declared.
예문:
"The company faced criticism for its unannounced policy changes."
"An unannounced witness appeared at the trial to provide new evidence."
사전 통보나 예고 없이 갑작스럽게 이루어지는
Occurring or arriving without prior notice or warning.
예문:
"The supervisor made an unannounced visit to the construction site."
"He prefers to travel unannounced to avoid any formal receptions."