I am borrowing from @dpworkin here whose description is very close to my own, with a couple of changes.
She must be a person of some accomplishment, emotionally available, and not afraid of vulnerability. She would be intelligent and have a great sense of humor and a quick wit, with a sarcastic bent, stylish, physically active, and for me, anyway, she would probably have to be post-menopausal or close to it, because women younger than that are not really appropriate for men my age.
I would add a couple of things. Very short would not work. I prefer taller. Slim is good, but not skinny. Sensual as described by @Just_Justine, “sensuality is everything and it is often quite rare today. When everyone is all fit, hard, and puffed up.”
@FutureMemory On a physical level she must smell good – whether it’s from perfume (small amount – I don’t want to smell her from more than a few feet away – excessive perfume is a huge turn off) or maybe just her bathing routine (scented body wash or whatever). A pleasant scent drives me wild! Smooth skin is also very very important.
I usually prefer the coloring of a brunette (not the white white skin of a blond or a person with very black hair), but, as for hair, I am also a fan of blonde highlights or blonde from a bottle.
Finally, someone of my spiritual and political bent…...and with a high libido.