unannounced [ˌʌnəˈnaʊnst]

例句:

• It sweeps in unannounced every seven to fourteen years.
  来自VOA
• He had just arrived unannounced from South America.
  他刚刚从南美来到这里，事先没有打招呼。
  
• She just turned up unannounced on my doorstep.
  她未打招呼就来到我家门口了。
  
• Having arrived unannounced for supper, we had to take potluck.
  由于没有提前通知我们要来吃晚饭, 我们只能吃些家常便饭.
  
• Lawyers say the previously unannounced hearing was standard procedure.
  来自VOA
• The monitors say they will make some unannounced visits.
  来自VOA