Chastisement is the act of scolding or punishing someone. If you talk back to your stern teacher, you won't be surprised by the chastisement that follows.
The noun chastisement usually means a verbal reprimand, like the chastisement a basketball coach might give his team after a terrible loss. It can also describe physical punishment, or a beating — when it's used in the Bible, that's almost always what it means. The Latin root of chastise is castigare, which means "to set or keep right," or "to make pure."