Definition.
A symbol is an image with an archetype — and therefore, a mystery — at its heart. Not limited to visual images, symbols express an idea that is not fully understandable or expressible. We may be able to interpret a symbol with some confidence, but the essence of a truly living symbol will always remain partly ineffable.
Consider the disembodied hands in Baba Yaga’s cottage in the Vasalisa story; they ring with the numinous, but their meaning, while interpretable in many ways, can never be completely understood.
Compare to sign.