In 2006, Tancredi was one of a number of dissenters at the IAU's meeting to establish the first definition of "planet." As an alternative to the IAU's draft proposal, which had included Pluto, its moon Charon and Ceres among the planets, Tancredi with his Uruguayan colleague Julio Ángel Fernández proposed a definition where they reserved the term "planet" only for those objects in the Solar System which had cleared their neighbourhoods of planetesimals, describing those objects which had not cleared their orbits yet retained a spherical shape as "planetoids."[5] The IAU's final definition incorporated much of Fernández and Tancredi's proposal, though the objects were christened "dwarf planets."[6]