Dictionary.net

In trademark law, a word or symbol commonly used to describe an entire type of product or service rather than to distinguish one product or service from another. An example is "raisin bran," used by several manufacturers of breakfast cereals to describe their products. Generic marks never receive protection because they don't serve the basic function of marks, which is to distinguish goods and services in the marketplace.

A legally unprotected, yet distinguishing mark, in the form of a symbol or a word. This mark definitively categorizes and defines a type of product or service. Some examples are name we all know well: Vaseline, Cellophane, Trampoline and Yoyo. Due to generic usage by consumers and competitors it refers to trademark names of goods and services that lost their trademark protection properties over time.