We found 30 dictionaries that define the word pion:

General (21 matching dictionaries)

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

Art (1 matching dictionary)

22. pion-: A Cross Reference of Latin and Greek Elements

Computing (1 matching dictionary)

23. pion: Encyclopedia

Medicine (1 matching dictionary)

24. pion: Medical dictionary

Miscellaneous (2 matching dictionaries)

25. pion, pion, pion: Terminology and Descriptions of Geneaological Words
26. PION: Acronym Finder

Science (3 matching dictionaries)

27. Pion: Eric Weisstein's World of Physics
28. Pion: Extragalactic Astronomy
29. Accelerator Glossary (No longer online)

Slang (1 matching dictionary)

30. Pion: Urban Dictionary

(Note: See pionic as well.)

Definitions from Wiktionary (pion) ▸ noun:  (physics) Any of three semistable mesons, having positive, negative or neutral charge, composed of up and down quarks/antiquarks. Similar: pi-meson, pi-plus, pionium, pi-minus, antipion, dipion, pi plus, pi minus, meson, hyperpion, more... Types: pi-meson, pi-zero, pi-plus, pi-minus, pi-zero-star, pi-zero-plus, more... Phrases: 2S7 Pion, more... Adjectives: neutral, two, one, negative, positive, single, soft, three, virtual, charged, multi Colors:     pink,     magenta,     fuchsia,     rose,     blush, more... ▸ Words similar to pion ▸ Usage examples for pion ▸ Idioms related to pion ▸ Wikipedia articles (New!) ▸ Popular adjectives describing pion ▸ Words that often appear near pion ▸ Rhymes of pion ▸ Invented words related to pion