It’s true that we often hear this word used in connection with business and the stock market, but anything can plummet.
An object can plummet to the earth from an airplane, for example. When I lived on the 44th floor, I often imagined how something would plummet to the ground if I threw it out the window. Of course, our windows didn’t open for security reasons. It was a strange way to live when I think about it now, I can’t imagine being unable to just pull open a window on a beautiful spring day!