What a man does (by stamping on it with his foot) after the blessings at a Jewish wedding, as a commemoration of the Temple in Jerusalem, which was destroyed in 68 or 70 of the Common Era. The idea is that even at the peak of our joy, we have to acknowledge the sadness and evil that persist in the world.
"Wasn't it a beautiful wedding?"
"Yes, they're just perfect for each other."
"I know. When he broke the glass, I cried."