O is for "The Devil's Dictionary" (No. 190 in a series)

The Devil's Dictionary is a satirical dictionary written by Ambrose Bierce (1842-c.1914, caricatured above by David Levine). Bierce was an American author who began the book as a newspaper serial. First published in 1906 as The Cynic's Word Book, it was retitled in 1911, using the name we know it by today, which is the title that Bierce preferred. Some of the definitions have not aged all that well, but many have. 

OPTIMISM, n. The doctrine, or belief, that everything is beautiful, including what is ugly, everything is good, especially the bad, and everything right that is wrong. It is held with greatest tenacity by those most accustomed to the mischance of falling into adversity, and is most acceptably expounded with the grin that apes a smile. Being a blind faith, it is inaccessible to the light of disproof -- an intellectual disorder, yielding to no treatment but death. It is hereditary, but fortunately not contagious.