We must have gone to the same school. Were you allowed to say, "(Word to be defined) is where," or "(Word to be defined) is when"?
Each of those phrasings was prohibited, along with using the root of the word to be defined in the definition.
No.
Not being able to use any form of a word to define it often forced us to get very creative. That rule makes sense, and it really helped me to understand what words mean.