Wallpaper
What it is:
Wallpaper is slang for a security with minimal to no market value.
How it works/Example:
Why it matters:
Following the Internet startup bust in the early 2000s, the stock of many web-based companies turned into wallpaper in a short span of time. The term doesn't only apply to stocks. For example, the impact of hyperinflation in Germany following World War I resulted in its currency becoming wallpaper.