Wiktionary
of a certain age
a. (context euphemistic lang=en chiefly of a person) old.
Usage examples of "of a certain age".
As you may remember if you are of a certain age and disposition, this was a quiz show—.
They were military men of a certain age, grizzled officers, who walked rather stiffly and seated themselves with circumspection.
Ask Germans of a certain age about how things change in a real war, or read diaries of Southerners in the Civil War.
The Trollocs came to kill or capture young men of a certain age who live near Emond’.
People of a certain age invariably remembered that cartoon character when they encountered the less regal but equally peevish George Woodard.
Suppose we were to take all the children of a certain age and tuck them away safe in this little bit of a mine?