If a man succeeds in signaling a high sexuality to a women, the woman might still treat him as a creep.
In which case he failed to signal "sexy" and (a common failure mode) signaled "creepy" instead.
It depends on how you define the term.
For a reasonable definition of sexy, the term refers to letting a woman feel sexual tension. If you talk about social interactions it's useful to have a word that refers to making another person feel sexual tension.
Of course you can define beautiful, attractive and sexy all the same way. Then you get a one dimensional model where Bob wants Alice with utility rating X. I don't think that's model is very useful to understanding how humans behave in mating situations.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.