Source : Webster's Revised Unabridged Dictionary (1913)

Mannerism \Man"ner*ism\, n. [Cf. F. mani['e]risme.]
   Adherence to a peculiar style or manner; a characteristic
   mode of action, bearing, or treatment, carried to excess,
   especially in literature or art.

         Mannerism is pardonable,and is sometimes even
         agreeable, when the manner, though vicious, is natural
         . . . . But a mannerism which does not sit easy on the
         mannerist, which has been adopted on principle, and
         which can be sustained only by constant effort, is
         always offensive.                        --Macaulay.

Source : WordNet®

mannerism
     n 1: a behavioral attribute that is distinctive and peculiar to
          an individual [syn: {idiosyncrasy}, {foible}]
     2: a deliberate pretense or exaggerated display [syn: {affectation},
         {pose}, {affectedness}]