Definition: Dwarf Planet: A Dwarf Planet actually has its definition based on the definition of a planet. While a planet has three criteria to meet, a dwarf planet only has to meet two of those criteria.
To be a dwarf planet, an object must (a) orbit the sun and (b) have a nearly round shape. Unlike a planet, it does not clear away objects in its neighborhood.
Two of the best known dwarf planets in our solar system are Ceres and Pluto.