Every child goes through the phase of discovering words that result in inmediate parental reactions. You know, adult words. My 5 year old said a huge one the other day and I almost fainted. The fact of the matter is they usually just repeat what they hear and don't really know what it means. The best approach is to ask them what they think it means. When they say they don't know, you have the choice to tell them the meaning if it's appropriate and explain why it's not alright for them to say this word or any other word that they don't know the definition to. This usually works.... Check out my site, it has behavior management of little ones and might help: http://psychmom.typepad.com/psychmomreflections