Don Quixote

Don Quixote, the title of a world-famous book written by Miguel Cervantes, in satire of the romances of chivalry with which his countrymen were so fascinated; the chief character of which gives title to it, a worthy gentleman of La Mancha, whose head is so turned by reading tales of knight-errantry, that he fancies he is a knight-errant himself, sallies forth in quest of adventures, and encounters them in the most commonplace incidents, one of his most ridiculous extravagancies being his tilting with the windmills, and the overweening regard he has for his Dulcinea del Tobosa.

Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)