1. not announced or made known beforehand

1. without prior notice or announcement

Examples

• The principal made an unannounced visit to our classroom.
• She arrived unannounced at the party.
• The company conducted unannounced inspections of the factory.
• He showed up unannounced at her doorstep.
• The test was unannounced, catching many students off guard.
• They made an unannounced change to the schedule.
• The celebrity appeared unannounced at the charity event.