We found 22 dictionaries that define the word planetary nebula:

General (14 matching dictionaries)

1. planetary nebula: Merriam-Webster
2. planetary nebula: Oxford Learner's Dictionaries
3. planetary nebula: American Heritage Dictionary of the English Language
4. planetary nebula: Collins English Dictionary
5. planetary nebula: Vocabulary.com
6. planetary nebula: Wordnik
7. planetary nebula: Wiktionary
8. planetary nebula: Infoplease Dictionary
9. planetary nebula: Dictionary.com
10. Planetary nebula: Wikipedia, the Free Encyclopedia
11. planetary nebula: Rhymezone
12. planetary nebula: FreeDictionary.org
13. planetary nebula: Mnemonic Dictionary
14. planetary nebula: TheFreeDictionary.com

Computing (1 matching dictionary)

15. planetary nebula: Encyclopedia

Medicine (1 matching dictionary)

16. planetary nebula: Medical dictionary

Miscellaneous (1 matching dictionary)

17. Encyclopedia of Graphic Symbols (No longer online)

Science (4 matching dictionaries)

18. Planetary Nebula: Eric Weisstein's World of Astronomy
19. Imagine the Universe! Dictionary (No longer online)
20. Planetary Nebula: Extragalactic Astronomy
21. PLANETARY NEBULA: Zoom Astronomy Glossary

Tech (1 matching dictionary)

22. High-Energy Astrophysics (No longer online)

(Note: See planetary_nebulas as well.)

Definitions from Wiktionary (planetary nebula) ▸ noun:  (astronomy) A nebulosity surrounding a dying red giant, consisting of material expelled by the star. Similar: planetary nebula nucleus, nebula, radio nebula, stellar nursery, supernova remnant, nova remnant, nebulium, nebularization, nubecula, stellar nova, more... Opposite: supernova, black hole, white dwarf Types: ring nebula, butterfly nebula, dumbbell nebula, helix nebula, cat's eye nebula, more... ▸ Words similar to planetary nebula ▸ Usage examples for planetary nebula ▸ Idioms related to planetary nebula ▸ Wikipedia articles (New!) ▸ Words that often appear near planetary nebula ▸ Rhymes of planetary nebula ▸ Invented words related to planetary nebula