From Der Spiegel:
Evelyn Zupke, die Aufsässige von der Insel Rügen, die mit der großen Klappe, hatte endlich Bruder und Schwestern im Geiste gefunden.
What does "Klappe" mean here? I looked at meanings in the dictionary, which are like "flap", "strap", "fly swat", but none of them seems to be something that should be on an island.