Nadine,
I've been coaching volleyball a long time and I've never heard that expression. The word "chuck" is sometimes used in place of "throw", which could be interpreted to mean either the act of setting, or to make a bad set. Whatever it means it is slang for something and it's probablly better to use a different phrase.

acctually, i think that to chuck a set means to not take the set and spike but volley...