A piece of
jewelry worn on the
ring finger made of low-grade gold and Cubic
Zirconium that looks similar to an
engagement/
wedding ring. Worn by unmarried
women (usually very
attractive or very
smart) on
college campuses informing many would-be
suitors they are not seeking a potential
SO.
These can be impossible to distinguish at a distance with the naked eye from real wedding or engagement rings as you have to talk to and get to know the female in a non-threatening way (very difficult as they can see a pending advance coming from a mile away).
This mind game tends to have a very high success rate on campuses (this is where my sister learned about the concept).