I can only speak for myself, and I hope my honesty does not offend. I mean no disrespect.
Sexiness is a complex thing, and the definition varies from person to person. I prefer a sex appeal that is understated, and even a bit accidental. Sexiness on a woman can be less intentional, and, in a setting where seduction is inappropriate, the effect can be intensified. At the office, the barest glimpse of panty lines beneath her pencil skirt... the visible bra straps beneath her elegant blouse as she removes her jacket... an accidental peek at her cleavage as she bends over to point something out on a print sheet, but her blouse is open just one button too low... a flash of her thigh as she sits down while wearing a skirt with a slit...
At a pool, or at the beach, a bikini wedgie is far more sexy than a thong or G-string which reveals too much. No, sexiness must always leave more to the imagination. As she emerges from the water after taking a relaxing swim, the sight of her nipples beneath the soaked one-piece or bikini top, that's sexy. If she doesn't shave her pussy, the sight of a dark bush beneath her bathing suit is a huge turn-on, just before she quickly grabs a beach towel to wrap around her waist. That's sexy. Why? Because it's an unintentional thing, rather than an overt attempt at seduction.
But a woman out in public, trying too hard to look sexy by wearing outfits best worn only in the bedroom makes her look like a cheap *******. Now, it's a popular look within the lifestyle for women ( single or married ) to dress as "trashy" as possible. It's a chance to whip out the bustier, the naughty lingerie, kinky corset, and, of course, the stiletto stripper heels. They see swinging events as an outlet for a powerful desire to release their inner "slut," or live out their "whore" fantasy. Hey, whatever floats your boat. But I pass these women by because I'm more turned on by contrast. I'm attracted to the wholesome-looking wife with a next-door neighbor appeal. She has a pure appearance that helps make her look slightly out of place at a swing party. To me, that's sexy. It's a fun reversal on expectation. But walking the streets looking like a whore is a turn-off because that's a woman who's trying too hard. It's like she's gone fishing down at the lake with grenades and a bazooka. Plus, it can scare some guys off because they're worried about catching an STD being with a woman who looks like she has sex at the drop of a dime, any time, and with almost anybody.
As always, Your Mileage May Vary.