A cougar, to me, is a woman 35-45 in her sexual prime. She is always on the hunt for that next great sex adventure. Generally that is applied to younger more energetic males, but it is not limited to them. The term carries some preconceptions. Mature, sexy, self confident, and knows what she wants and how she wants it. Even if she lets her partner make most of the choices, which would be extrememly rare, the cougar remains in control.
I know three women that fall under the title of cougar. They have husbands the same age as them. The cougar is hitting her sexual peek and her husbands had his 20 years ago. Naturally the cougar is not satisfies and feels the need to hunt. As far as I know only one of the three has actually gone outside their marrage to satisfy their sexual hunger. I "know" because she has suduced me a few times in the past. The other two are content to flirt and revell in the attention they get.