unannounced

for overseas drug plants.In the US, FDA investigators arrive unannouncedto do surprise inspections.

rigorous oversight,including unannounced inspections and systematic testing of drugs.Rigorous oversight means that regulators don't just look at printouts of data

And you have to respond to a report of child abuse.You walk into a home, unannounced, unexpected, certainly uninvited.The first thing you see is a mattress in the middle of the room, on the floor.