Found numerous answers to your question using Google. Here is one I found at wikipedia.com
quote:
"A plutoid is a trans-Neptunian dwarf planet. The International Astronomical Union (IAU) developed this category of astronomical objects as a consequence of its 2006 resolution defining the word "planet". The IAU's formal definition of 'plutoid,' announced 11 June 2008, is:
Plutoids are celestial bodies in orbit around the Sun at a semimajor axis greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit. Satellites of plutoids are not plutoids themselves.[1]
Accordingly, plutoids can be thought of as the intersection of the set of dwarf planets and the set of trans-Neptunian objects. As of 2008, Pluto, Eris and Makemake are the only objects classified as plutoids. Upwards of 41 more bodies known today may yet be determined to meet the definition."
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