a penny that is put in a machine that imprints it with a word or design. Generally it is given as a gift from one person to another, usually boy to girl or vice versa. It generally signifies eternal friendship but nothing more, like a relationship. The receiver usually accepts the gift but then enters a state of depression behind closed doors because he wants to have a relationship.
Marissa just gave me a smashed penny and I'm pissed because I want to be more than friends; now I'm stuck in the best friend zone.