It doesn't even have any referents to reality. It's not even a statement about whatever "reality" we live in, to the best of my knowledge. If it does mean five-leggedness of unicorn creatures with the implication of the existence of possible-existence of such creatures in reality, then it is false, but it's inconsistent with what we know of reality, since there's no way such a creature would exist.

...I think, anyway. Not quite sure about that second part.