I have a new method for testing definitions. Read a definiens to someone, out of context, and ask her what she thinks the definiendum is. If she doesn't come up with something pretty close to the definiendum, you've got reason to think the definition is bad.
One can also do this as a thought experiment, though it's probably less effective that way. What does "justified true belief with no false lemmas" define? Answer: nothing other than justified true belief with no false lemmas. (Maybe you were trying to define knowledge?) What does "Sex between two people at least one of whom is married and who are not married to each other" define? Answer: adultery. (Right!)