We found 31 dictionaries that define the word thorium:

General (20 matching dictionaries)

1. thorium: Merriam-Webster
2. thorium: Oxford Learner's Dictionaries
3. thorium: American Heritage Dictionary of the English Language
4. thorium: Collins English Dictionary
5. thorium: Vocabulary.com
6. Thorium, thorium: Wordnik
7. thorium: Wiktionary
8. thorium: Webster's New World College Dictionary, 4th Ed.
9. thorium: The Wordsmyth English Dictionary-Thesaurus
10. thorium: Infoplease Dictionary
11. thorium: Dictionary.com
12. thorium: Online Etymology Dictionary
13. Thorium: Wikipedia, the Free Encyclopedia
14. Thorium: Online Plain Text English Dictionary
15. thorium: Webster's Revised Unabridged, 1913 Edition
16. thorium: Rhymezone
17. Thorium: AllWords.com Multi-Lingual Dictionary
18. thorium: FreeDictionary.org
19. thorium: Mnemonic Dictionary
20. thorium: TheFreeDictionary.com

Business (2 matching dictionaries)

21. Thorium: Energy Dictionary
22. thorium: Financial dictionary

Computing (1 matching dictionary)

23. thorium: Encyclopedia

Medicine (5 matching dictionaries)

24. thorium: Merriam-Webster Medical Dictionary
25. Dorland's Illustrated Medical Dictionary (No longer online)
26. Medical Dictionary (No longer online)
27. online medical dictionary (No longer online)
28. thorium: Medical dictionary

Science (2 matching dictionaries)

29. Thorium: Extragalactic Astronomy
30. Thorium, thorium: WebElements Periodic Table of the Elements

Tech (1 matching dictionary)

31. Schlumberger Oilfield Glossary (No longer online)

Definitions from Wiktionary (thorium) ▸ noun:  A chemical element (symbol Th) with atomic number 90: a weakly radioactive, malleable, moderately hard silvery metal that tarnishes black when exposed to air. Similar: Th, atomic number 90, thorinum, thulium, thorium emanation, thallium, thorin, thorite, thoria, terbium, more... Types: actinide, radioactive, transuranic, superheavy, more... Phrases: Thorium dioxide, thorium oxide, thorium nitrate, thorium series, thorium compounds, more... Adjectives: natural, metallic, pure, uranium, ordinary, radioactive, more, reduced, separate, fertile, little Colors:     silver,     gray,     charcoal,     graphite,     gunmetal, more... ▸ Word origin ▸ Words similar to thorium ▸ Usage examples for thorium ▸ Idioms related to thorium ▸ Wikipedia articles (New!) ▸ Popular adjectives describing thorium ▸ Words that often appear near thorium ▸ Rhymes of thorium ▸ Invented words related to thorium