Silver fox
An older man with gray or silver hair who is still seriously attractive, often more than ever: well groomed, stylish and wearing his age like an upgrade.

A silver fox is an older man with gray or silver hair who is still seriously attractive, often more than he was at thirty. Salt-and-pepper beard, well-cut hair gone white at the temples, a good jacket, a bit of a twinkle: the silver fox wears his age like an upgrade.
The word is pure compliment. It is not just "older guy": it says the gray is part of the appeal, and that the man knows it. It is also general slang, not only gay: straight women use it about George Clooney types all the time. But gay men have made it one of their favorite labels for the handsome older man.
Where it comes from
The image is simple: a fox is sleek, clever and a little sly, and "foxy" has long meant sexy. Add silver for the hair and you have a sharp, good-looking older man. Green's Dictionary of Slang defines it exactly that way. We have not found a reliable first date for the phrase, so we will not give one.
Silver fox, daddy, polar bear
The three older-man labels do different jobs. A daddy is about age plus attitude: protective, in charge, often with a sexual role to match. A polar bear is about the body: a big, hairy bear who has gone white. A silver fox is about looks and style: usually leaner, well groomed and elegant, more tailored suit than flannel shirt. A man can be all three at once, and some lucky ones are.
How it is used today
On the apps it is both a self-label and a type: men in their fifties and sixties call themselves silver foxes with good reason, and younger men list them among the types they like. In porn the tag covers handsome older performers, often in daddy porn, and the age-gap pairing with a younger man is a classic. Men who chase them have their own name, a daddy chaser.
In a gay world that can be harsh about age, the silver fox is a cheerful counterexample: gray hair, deep lines and all, he is the one people turn around to look at.
Related terms
Sources 1
- Green, Jonathon. "silver fox, n." (under silver, adj.). Green's Dictionary of Slang, online edition. https://greensdictofslang.com/entry/2an7aua#duc5tka