What does gild gold mean?

well, the verb "gild" can mean to cover something in a thin layer of gold, or can mean to decorate something in a way that makes it look more expensive than it is, or can also mean to decorate something that is already sufficiently decorated (like "gild the lily", making the point that a flower doesn't need further decoration). So "gild gold" would probably mean to either do something to it that made it look like a purer form of gold than it is (so making it look deceptively expensive) or simply to decorate something that is already beautiful because it is gold. hope this helps.