Wiktionary
n. A laughing matter amongst a group of people, about something customary.
Usage examples of "standing joke".
It had been a standing joke among her male offspring that Mom could walk unescorted into any biker bar in the world and simply by her bearing and appearance cause all ongoing fistfights to be instantly suspended, all grubby elbows to be removed from the bar, postures to straighten, salty language to be choked off.
I didn't know whether or not this Hilda from Misery Benefits had been depressed, but it had become a standing joke between us.
Sphrantzes' wretched coin- age was a standing joke in his opponent's army.
The doctor, whether from lack of means or because he did not like to part from his young wife in the early days of their marriage, took her about with him wherever the hussar regiment went and his jealousy had become a standing joke among the hussar officers.
He almost never lost a wager on a game, and it was a standing joke that professional gamblers consulted him on the line for an important game.