Definitions of convertible:

• noun:   a car that has top that can be folded or removed
• noun:   a sofa that can be converted into a bed
• noun:   a corporate security (usually bonds or preferred stock) that can be exchanged for another form of security (usually common stock)
• adjective:   capable of being changed in substance as if by alchemy
• adjective:   capable of being exchanged for or replaced by something of equal value

  Example: "Convertible securities"

• adjective:   designed to be changed from one use or form to another

  Example: "A convertible sofa"