In a philosophical discussion, you should call a term "ambiguous" when and only when the expression has more than one acceptable meaning.

For instance, "bank" is ambiguous (river bank, Bank of Boston).

Also, sentences can be ambiguous, as in "Flying planes can be dangerous." Is it the activity of flying which is dangerous, or is it the planes which are dangerous?

Or: "Every child loves a clown." Does this mean there is one lucky clown that all the children love? Or does it mean that for each child, there is a particular clown which he or she loves (but not necessarily the same clown for each child)? Or does it mean that every child is favorably disposed to clowns in general?

You should not call an expression "ambiguous" just because different people have different views or theories about it. Different people have different views about what it means to be good, but that doesn't yet show that the expression "good" is ambiguous. It just shows that there's some controversy over what "good" means.

Nor should you call an expression "ambiguous" just because it's vague, or imprecise, or difficult to know what the correct philosophical theory of it is.

When an argument illegitimately trades on an ambiguity, we say that the argument equivocates.