Sure, the proposition that "penises are vaginas travelling faster than the speed of light" is perfectly coherent. Vaginas and penises are perfectly well-defined, and the notion of a penis travelling faster than the speed of light is, while not considered possible by any existing physical models, is entirely logically sensible.

It remains to determine whether vaginas are, in fact, penises travelling faster than the speed of light. The short answer is no, since anything travelling faster than the speed of light would be travelling faster than the speed of light, and vaginas typically travel subluminally. Thus, we have proven this well-formed statement false.

Now we're getting somewhere!

I realize that we're all programmers here, and that we live and die by unambiguous semantics. But human languages are awash in ambiguity and borderline nonsense, and the only thing holding it all together are some shared concepts and idioms. The disjoint between the clarity of science and the ambiguity of human communication is really interesting, and by that token something can be both incoherent and rich with meaning (though obviously this isn't always the case).