In United States trademark law, Abercrombie & Fitch Co. v. Hunting World has defined the framework of trademark distinctiveness. In the case, trademarks are divided into categories which have different degrees of protection.
A descriptive mark is one of such categories. It defines a term with a dictionary meaning which is used in connection with products or services directly related to that meaning.
An example might be Salty used in connection with saltine crackers or anchovies. Such terms are not registrable unless it can be shown that distinctive character has been established in the term through extensive use in the marketplace. Lektronic was famously refused protection by the USPTO on the grounds of being descriptive for electronic goods.
Example of descriptive trademarks are: