About 2 minutes of research on google reveals that when straight women say they’re feeling sexy, they mean they think they can turn someone else on. When straight men say they’re feeling sexy, they mean they’re feeling horny.
In the middle of the night, I had this epiphany that I communicated to my friend in gchat in the morning.
Me: Oh my god, I just had an epiphany. So like, I date all these people who express an asexual masculinity who are only able to express their sexuality through attraction to me.
Friend: This is not a coherent epiphany. Learn to write, plz.
Me: Ok. Ok – so, what I mean is, when I date people, I’m responsible for bringing all the sexual energy. Like, I have to look sexual enough to turn *them* on, but also have to be horny enough to be turned on *by* them when they’re not even trying to impress me.
Friend: http://www.reactiongifs.com/wp-content/uploads/2011/09/mind_blown.gif
Friend: Also, you are very smart and pretty, and have been looking very in-shape lately.
(May not be transcribed exactly.)
One of the marginally irritating features of my life, at least as a woman in her 20s (soon to be 30s,) is that people *always* perceive me as sexual. I’ve been sick for months, and regularly go out in vomit colored egg sweatshirts, and I still propositioned nearly daily. I have a whole setup of sun glasses and ear phones to block out the world and signal DON’T TALK TO ME when I’m walking down the street because it’s a big problem in my life.
I have talked to some of my male SF programmer friends, and the way they describe walking down the streets is totally different. Words like “ignored” and “lonely” come up a lot. And, that sucks. I can’t even really imagine what it’s like to be honest.
But what happens if I start dating someone who expresses an asexual masculinity (i.e. they’re masculine, but repress aspects of themselves that may be read as sexual – “business casual” male is a key example) is that, for the first time in a long time, they have a place to express their sexuality. But, it’s completely tied to *my* sexuality, it doesn’t stand alone.
(On a side note – I don’t mean to just call out men. I see this sometimes with the dapper/vintage masculine lesbian look. Personally, I find it to be a strangely asexual due to its historical associations, but it could just be me.)
And, on some level, society is hard on men in this way. But, on another level, many men have chosen *respectability* over *sexuality*. And, that’s fine – but, if you’ve chosen to be respectable rather than sexual, you have to anticipate that this may have an affect on the people you date. Have you heard of the low-libido crisis in American women lately? It’s always blamed on women (they work too much! they’re too tired! birth control!)
But, how many men do you know that put effort into being sexy? Do you think men being completely uninterested in impressing women could be linked to women being uninterested in them? (Or, they want to impress women with their awesome career – the adult version of impressing that popular girl in high school with your good grades.)
Did you know, if you’re a woman, dying your hair blonde can vastly increase the number of responses you get on a dating website? It’s not because men prefer blondes (or, so I tell myself as a brunette.) It’s because dying your hair blonde signals something. Something sexual. Similarly, a motorcycle or stupid hat can do the same thing for a guy.
(Don’t actually get that hat.)
Love and Void 
This kinda blew my mind. I never really thought about how the word “sexy” is used. What’s interesting — and you can blame this on my inflated ego — is I *always* feel sexy in the feminine sense. I always feel theoretically capable of turning someone on unless I’m really tired or physically ill. I’ve no idea how universal this is, but maybe it’s why men don’t typically think of needing to use signals in the way you describe — they think of feeling “sexy” as too obvious to mention. They’re just waiting to read the signals of a potential mate. They assume there will be interest and in a sense are acting as predators, reading the signals of their prey.
In blue-collar culture there are a handful of male sex signals — tattoos, a sleeveless shirt/vest to show off the results of gym membership, ownership of weapons, obviously the motorcycle / ATV / boat, the outline of the pin-up girl used as a car decal — but most of these also require wealth and thus are also a signal for financial success. I can’t think of a single example that solely signals sexuality like the female example of cleavage or hair color. Hmm.
I have literally no idea of how to go about putting in effort to be sexy. I wouldn’t know where to start, barring the obvious “dress in nice tight clothes”, “maintain good hygiene”, and “be in good physical shape”.