cougar
n. A middle-aged woman who seeks sexual or romantic relationships with younger men.
Examples
2010
Speaking to The Sunday Telegraph during Harper's Bazaar's Women of the Year Awards, where she won a prize for Role Model of the Year, Thompson said: "It's easy to be flattered, but I am no cougar. I've had a lot of male attention here from budding young actors asking about getting on in show business…It got me thinking about the cougar thing. I am a happily married woman, but, even if I was single, I wouldn't be up for it."
—Richard Eden, “Emma Thompson calls Hollywood actresses who take younger partners 'predatory',” The Sunday Telegraph, November 07, 2010
2010
Besides being dressed in a tight pair of jeans or (weather permitting) body-hugging dress, the cougar can be identified by three key characteristics. First, you'll notice that make-up has been liberally applied to the mouth and eye area. Second, her clothes will be cloaked in a heavy veil of overly floral perfume and, third, quite unlike the younger members of the female species, she'll have no qualms about getting raging drunk.
—Thomas Falkiner, “Notes from the field,” Sunday Times (South Africa), October 17, 2010
2000 (earliest)
On his way back to our table George had been stopped by a woman, one of several standing at the bar who tilted forward because of their high heels. This concerned John. "David, you'd better save George. He's been caught by a cougar." "What's that?" "A woman of a certain age looking for a man of a certain income."
—“The Pursuit of happiness,” The Globe and Mail, January 28, 2000