Here are a few possibilities:
* Individual expression: The person might be using it as a unique way to express their own beliefs or feelings.
* Art or fashion statement: It could be a temporary tattoo, a sticker, or a design used for aesthetic purposes.
* Reference to a specific subculture or group: It's possible that a specific group or community uses it as a symbol, but it's not widely known.
If you're curious about its meaning, it's best to ask the person directly!