What does “größenwahnsinnig” mean in German?

Mocking billionaires' plans to visit Mars, this comedian calls such stunts größenwahnsinnige Expeditionen — “megalomaniac expeditions.” The adjective comes from Größenwahn, a compound of Größe (“size, greatness”) and Wahn (“delusion, madness”): literally “size-delusion.” It’s German’s blunt, memorable word for an inflated, almost pathological sense of one’s own importance or capability.

Größenwahn has been documented since the 19th century and is still the standard clinical and everyday term for megalomania, alongside near-synonyms like Gigantomanie. The joke in this clip works because it puts real astronauts' caution against the größenwahnsinnig confidence of billionaires chasing Mars or, earlier, the doomed Titan submersible — ambition with the delusion built right into the word.