The term "convertible" has several meanings, depending on its context.
1) In a general sense, it refers to something that can be converted from one form or use to another. For example, a convertible car is one that can have its top lowered or raised to switch between an open-air driving experience and protection from the elements.
2) In finance, "convertible" typically describes a type of security that gives the holder the option to trade it for another asset, usually stocks, at a predetermined price. A convertible bond is one such example where the issuer agrees to pay back the investor's principal amount after a certain period and provides the right to exchange the bond for common shares of the company.
3) In fashion, "convertible" refers to clothing items that can be easily transformed from one style or use to another through adjustments or removable parts. For example, a convertible dress is one with multiple ways of wearing it such as being able to change its length, shape or even adding sleeves or removing them.