Convertible Preferred Stock

What Does Convertible Preferred Stock Mean?
Preferred stock that includes an option for the holder to convert the preferred shares into a fixed number of common shares, usually anytime after a predetermined date. 

Also known as "convertible preferred shares".

Investopedia explains Convertible Preferred Stock
Most convertible preferred stock is exchanged at the request of the shareholder, but sometimes there is a provision that allows the company (or issuer) to force conversion. The value of convertible common stock is ultimately based on the performance (or lack thereof) of the common stock.