The Collaborative International Dictionary of English v.0.48:

Quixotism \Quix"ot*ism\ (kw[i^]ks"[o^]t*[i^]z'm), n.
   That form of 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. See quixotic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

quixotism
    n 1: quixotic (romantic and impractical) behavior [syn: knight
         errantry, quixotism]