An Entity Class is a stereotype of a class that is specified in UML Extensions for Business Modeling. It can be shown as a regular class rectangle with stereotype of "entity", or as this icon:

An entity class is a class that is passive; that is, it does not initiate interactions on its own. An entity object can participate in many different Use Case realizations and usually outlives any single interaction. In business modeling entities represent objects that workers access, inspect, manipulate, produce, and so on. Entity objects provide the basis for sharing among workers participating in different Use Case realizations.

To draw an entity class on a Use Case diagram by selecting the Entity icon from the tools menu.

See also Changing from icon view to class view.