Wiktionary:Word of the day/September 30

1. (Greek mythology, Roman mythology) Of or relating to Pluto, the Greek and Roman god of the underworld; demonic, infernal.
2. (by extension) Of, relating to, or having characteristics associated with the underworld; dark, gloomy; mournful.
3. (by extension, geology) Synonym of plutonic (“of or pertaining to rocks formed deep in the Earth's crust, rather than by volcanoes at the surface of the Earth”).
4. (by extension, geology, historical) Synonym of plutonic (“of, pertaining to, or supporting plutonism, the theory that the rocks of the Earth were formed in fire by volcanic activity, with a continuing gradual process of weathering and erosion, then deposited on the sea bed, re-formed into layers of sedimentary rock by heat and pressure, and raised again”)
5. (astrology) Pertaining to the astrological influence of Pluto, formerly regarded as a planet.
6. (astronomy) Of or relating to the dwarf planet Pluto.

To mark the premiere of English composer Gustav Holst’s orchestral suite The Planets on 29 September 1918, we are featuring a series of words relating to the planets in the Solar System. Although Pluto was discovered four years before Holst’s death, he never wrote a movement for what was then thought to be a new planet (Pluto is now regarded as a dwarf planet). However, Colin Matthews composed a movement called Pluto, the Renewer 25 years ago in 2000.