What is Mischief?

Legal Definition
Mischief or malicious mischief is the specific name for different criminal offenses in a number of different jurisdictions. While the wrongful acts will often involve what is popularly described as vandalism there can be a legal differentiation between the two. The etymology of the word comes from Old French meschief, which means "misfortune", from meschever, "to end badly".
-- Wikipedia
Legal Definition
In legislative parlance, the word is often used to signify the evil or danger which a statute is intended to cure or avoid. In the phrase "malicious mischief," (which see,) it imports a wanton or reckless injury to persons or property.
-- Black's Law Dictionary
Legal Definition
-- Ballentine's Law Dictionary