Unannounced means happening without any warning or advance notice. When something arrives unannounced, it shows up unexpectedly, catching people by surprise.

An unannounced visitor knocks on your door when you weren't expecting anyone. An unannounced quiz at school means the teacher didn't tell the class it was coming. A pop star might make an unannounced appearance at a concert, thrilling fans who had no idea she'd be there.

The word often describes situations where someone could have given warning but chose not to, or where circumstances made advance notice impossible. If your grandparents drop by unannounced, they simply decided to visit without calling first. If a storm arrives unannounced, weather forecasters didn't predict it.

Sometimes unannounced arrivals are pleasant surprises, like an unexpected snow day. Other times they're inconvenient, like when fire drills happen without warning. Either way, unannounced captures that moment when something just appears, ready or not.