We found 21 dictionaries that define the word free radicals:

General (7 matching dictionaries)

1. free radicals: Merriam-Webster
2. free radicals: Collins English Dictionary
3. free radicals: Vocabulary.com
4. free radicals: Cambridge Advanced Learner's Dictionary
5. free radicals: Wiktionary
6. Free Radicals (band), Free Radicals (film), Free Radicals (short story), Free Radicals, Free radicals: Wikipedia, the Free Encyclopedia
7. Free radicals: TheFreeDictionary.com

Art (1 matching dictionary)

8. Free Radicals: Health & Beauty Glossary

Computing (1 matching dictionary)

9. Free radicals: Encyclopedia

Medicine (7 matching dictionaries)

10. free radicals: Merriam-Webster Medical Dictionary
11. Medical Dictionary (No longer online)
12. Breast Cancer Talking Dictionary (No longer online)
13. Free radicals: Merck Manuals
14. online medical dictionary (No longer online)
15. free radicals: Medical dictionary
16. WeMove Glossary of Terms (No longer online)

Science (1 matching dictionary)

17. Atmospheric Chemistry and Air Quality (No longer online)

Slang (1 matching dictionary)

18. Free Radicals: Urban Dictionary

Sports (1 matching dictionary)

19. Free Radicals: Body Building

Tech (2 matching dictionaries)

20. Glossary of Composite Terms (No longer online)
21. Free Radicals: Beauty & Health Glossary

(Note: See free_radical as well.)

Definitions from Wiktionary (free radical) ▸ noun:  (chemistry, physics) A molecule, ion or atom that has one or more unpaired electrons, and which is generally highly reactive (and therefore often occurs only as a transient species). ▸ Also see free_radical Opposite: antioxidants, stable molecules, non-radicals ▸ Words similar to free radicals ▸ Usage examples for free radicals ▸ Idioms related to free radicals ▸ Wikipedia articles (New!) ▸ Words that often appear near free radicals ▸ Rhymes of free radicals ▸ Invented words related to free radicals