In bocca al lupo (pronounced [im ˈbokka al ˈluːpo], "into the mouth of the wolf") is an Italian idiom originally used in opera and theatre to wish a performer good luck prior to a performance. The standard response is crepi il lupo! ([ˈkrɛːpi il ˈluːpo], "may the wolf die") or, more commonly, simply crepi! ("may it die").
Equivalent to the English actor's idiom break a leg, the expression reflects a theatrical superstition in which wishing a person "good luck" is considered bad luck. The expression is commonly used in Italy off stage, as superstitions and customs travel through other professions and then into common use, and it can sometimes be heard outside of Italy.