A Zeppelin is a type of airship. Airships are aircraft that float in air, because they are filled with a lightweight gas. A Zeppelin is a dirigible, which means it is a rigid airship, but can be moved around by itself. It was developed by Count Ferdinand von Zeppelin, in the early 20th century. The name Zeppelin is now used as a common name for all rigid airships. Zeppelins were used in the First World War. In the Second World War the Nazis largely used them for propaganda purposes.