Jennifer Lopez's latest video is not of the musical variety. Instead, it promotes Teeology, the T-shirt range Lopez "cur-ates", which means . . . actually, I've no idea what it means to "curate a T-shirt range", but let's not get caught up in that; conveniently, it isn't relevant.
What is relevant is that in the video Lopez models a series of jersey tops emblazoned with legends such as "Je suis fraiche" ("I'm cool"), "I've Got A Secret" and "Truly Madly Deeply In Love".
She wears them well: convincingly, effortlessly, minxishly and with absolutely no concession to the fact that she's 43, older than one might imagine the wearers of such T-shirts should be.
Lopez is a cougar. But not in the way you're thinking. The term, introduced to contemporary vernacular as a description of women in their late 30s and 40s who make a habit of dating boys considerably younger than they are, and which gained particular currency as a consequence of the rise to fame of One Direction's Harry Styles, has evolved.
It has lost its sneering, derogatory, somewhat prurient undertones and gained an aspirational quality.
"Cougar" now denotes a specific sort of sexiness; it's applied to the 40-something woman who has no particular interest in pulling younger men but could, if she chose to.
Look around you. They're everywhere. I'm one. I'm 40, I wear leather trousers, I'm a cougar, but it's not what you think.
Like all cougars, I consider leather trousers an everyday basic. I'll throw a pair on (with Cuban-heeled ankle boots and a grey marl T-shirt) and wear them as thoughtlessly as I would the skinny jeans I wear when I'm not wearing leather trousers. Which isn't often.
My cougar cohorts and I like all forms of slimline legwear, but we especially like the shiny kind.
A 47-year-old cougar fashion editor friend of mine recently told me (as she accompanied me to a birthday party while dressed, magnificently, in PVC-coated leggings and a tuxedo jacket) that "an entire section of my wardrobe is now dedicated to disco pants"; by which she means high-waisted, extremely tight trousers finished in either sequins, or with a satin sheen, or a tuxedo stripe, or wrought entirely of leather or suede.
Cougars wear skirts grudgingly, but when we do, we'll opt for knee-length pencil skirts – never, ever minis; and we will do it because we think we should make some effort to look more like French fashion editor and cougar icon Carine Roitfeld . . . ditto French Vogue editor Emmanuelle Alt.
All of which might go some way to explaining Marks & Spencer's recent downturn in profits. M&S does not cater well for cougars; too much co-ordinated machine washable lambswool, not enough leather, you see. No wonder we all end up in Zara. Having said that, the fact that M&S is now stocking leather trousers might suggest it's on to us.
This is not to say that cougars are mutton dressed as lamb. They're quite the opposite. Cougars do not try to look younger than they are, because they do not want to look younger than they are.
They are testimony to the fact that notions of age appropriateness are changing, that the long-standing belief that women become invisible after their mid-30s – unnoticed, unremarked upon, irrelevant – and must therefore disguise their ageing, is simply no longer true.
Cougar style isn't about 40 being the new 30, or midlife being the new teenage. It's more about 40 being a fine old thing in its own right – an appealing, empowered thing that doesn't actively seek male approval, but often ends up getting it anyway – and that the same can be said of 50 and 60.
Cougars understand there's an innate appeal in being their age – as long as they dress it correctly. While they approve of red lipstick and black liquid eyeliner, they do not wear lip gloss (too Wag for words); and they do not really approve of over-bleached blonde hair (unless it's very short).
Hair, if it's blow dried, must never look too big or too perfect. Cougars never wear stripper heels, fake tan or pink. Cougars are well groomed, but never pristine: while their eyebrows will always be neat, their mascara will probably be smudged.
Cougars expose flesh judiciously, and quite rarely. Legs, backs and arms (if well-toned and not fake tanned) are acceptable (but never all three in combination). Generally, cougars are much more interested in showcasing their well-maintained bottoms, which is why they're so fond of the tight-fitting trousers.
If cougars are not mutton dressed as lamb, nor are they yummy mummies. They are politically opposed to chintz, prints, pastels and the Boden catalogue. They'll only indulge a court shoe if they have a vicious point on the toe, and some patented embellishment. Cougars do not aim to be pretty, girlish or passively feminine; they want to look vampish and predatory, even if they aren't. Cougars never wear cardigans.
Cougars have many icons: Lopez, Roitfeld, but also Michelle Obama (who would surely be wearing leather trousers if she weren't a First Lady), Samantha Cameron (ditto), Livia Firth (wife of Colin), Natalie Massenet, comedian Tina Fey, Stella McCartney, BBC newsreader Emily Maitlis, French politician Rachida Dati and the partner of Francois Hollande, Valerie Trierweiler.
Also Helena Christensen (cougars forgave her for modelling in the Boden catalogue because they understand the compulsion to make money). Madonna, Helen Mirren, Carole Middleton and Joanna Lumley demonstrate how it might be done in your 50s and 60s.
At the other end of the spectrum we're seeing increasing incidences of younger women prematurely co-opting cougar styling.
Such is its influence. Kristen Stewart did it last week, while promoting the final instalment of the Twilight saga; Kate Moss, at 38 – very nearly 39 – is an honorary cougar. And so is Nigella Lawson, who looks great and doesn't give a damn.
Cougar style is a third way; it isn't mutton dressed as lamb and it isn't frumpy middle age. Your first step towards it is to try on a pair of leather trousers. Go on. You might just like it. I do.