The story
Etymology from Wiktionary, CC BY-SA 4.0.
Today it means: A form of idealism and delusion which leads to extravagant and absurd undertakings or sacrifices in obedience to a morbidly romantic ideal of duty or honor, as illustrated by the exploits of Don Quixote in knight-errantry. Full definition →
Etymology from Wiktionary, CC BY-SA 4.0.