Definition of "mannerism"

mannerism¹

/ˈmænəˌɹɪzəm/

noun
countable and uncountable, plural mannerisms
1. A noticeable personal habit, a verbal or other (often, but not necessarily unconscious) habitual behavior peculiar to an individual.
  Quotations
  In the old days, to my commonplace and unobserving mind, he gave no evidences of genius whatsoever. He never read me any of his manuscripts, […], and therefore my lack of detection of his promise may in some degree be pardoned. But he had then none of the oddities and mannerisms which I hold to be inseparable from genius, and which struck my attention in after days when I came in contact with the Celebrity.
  1897 December (indicated as 1898), Winston Churchill, chapter I, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd.
2. Exaggerated or affected style in art, speech, or other behavior.

mannerism²

/ˈmænəˌɹɪzəm/

noun
countable and uncountable, plural mannerisms
1. (art, literature) In literature, an ostentatious and unnatural style of the second half of the sixteenth century. In the contemporary criticism, described as a negation of the classicist equilibrium, pre-Baroque, and deforming expressiveness.
2. (art, literature) In fine art, a style that is inspired by previous models, aiming to reproduce subjects in an expressive language.