The term Dwarf Planet was coined to apply to solar system objects that were like planets but smaller. Planets and dwarf planets are massive enough to settle into a sphere, but a "full" planet is also massive enough to clear out a lane through which it orbits. Dwarf planet is a subtype of a Minor Planet, essentially any solar system object larger than a Meteoroid that is not a Comet, Moon, or "full" planet.
In particular, the term dwarf planet was coined for Pluto when similar objects became known. The other known examples are Ceres, Haumea, Makemake, and Eris. Other observed, but poorly-resolved bodies may fit the description and there may be more as yet unseen.
International Astronomical Union (IAU)