until Emanuella delivers the It. verdict, here's OED2 chiming in:
[It.]

Ease of manner, studied carelessness; the appearance of acting or being done without effort; spec. of literary style or performance.

1957 N. FRYE Anat. Criticism 93 The quality that the Italian critics called sprezzatura. 1960 E. H. GOMBRICH Art & Illusion III. vi. 193 Sprezzatura, the nonchalance which marks the perfect courtier and the perfect artist. 1960 Spectator 14 Oct. 569 The style governed by sprezzatura, dash and mandarin neoclassicism. 1973 Times Lit. Suppl. 14 Sept. 1063/2 Literary fashion and his own aristocratic sprezzatura demanded that he affect an unconcern.