The term dwarf planet was coined to apply to solar system objects that are like planets but smaller. Planets and dwarf planets are massive enough to settle into a sphere, but a "full/true/official" planet (per IAU) is also massive enough to clear out a lane through which it orbits (a criteria termed clearing the neighborhood). 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.