Quixotic describes someone or something that is idealistic and impractical, often romantically so. The word originates from the Spanish novel *Don Quixote* by Miguel de Cervantes. The protagonist, Don Quixote, is a knight-errant who sets out on a series of adventures based on his romantic ideals of chivalry, despite the fact that these ideals are unrealistic and ultimately lead to his downfall.
So, if someone is described as quixotic, it means they have high but impractical sentiments and aims, just like Don Quixote.