We found 17 dictionaries that define the word quarter tone:

General (14 matching dictionaries)

1. quarter tone: Merriam-Webster
2. quarter-tone: Oxford Learner's Dictionaries
3. quarter tone: Collins English Dictionary
4. quarter-tone, quarter tone: Vocabulary.com
5. quarter-tone: Wordnik
6. quarter tone: Wiktionary
7. quarter tone: The Wordsmyth English Dictionary-Thesaurus
8. quarter tone: Infoplease Dictionary
9. quarter-tone, quarter tone: Dictionary.com
10. Quarter tone: Wikipedia, the Free Encyclopedia
11. quarter-tone, quarter tone: Rhymezone
12. quarter-tone, quarter tone: FreeDictionary.org
13. quarter-tone, quarter tone: Mnemonic Dictionary
14. quarter-tone, quarter tone: TheFreeDictionary.com

Art (1 matching dictionary)

15. Virginia Tech Multimedia Music Dictionary (No longer online)

Science (1 matching dictionary)

16. How Many? A Dictionary of Units of Measurement (No longer online)

Tech (1 matching dictionary)

17. Sweetwater Music (No longer online)

(Note: See quarter_tones as well.)

Definitions from Wiktionary (quarter tone) ▸ noun:  (music) The musical interval equal to one quarter of a tone or 1/24 of an octave; half a semitone. Similar: quartertone, quarter-tone, half tone, halftone, half-tone, semitone, whole tone, quadtone, cent, half-step, more... ▸ Words similar to quarter tone ▸ Usage examples for quarter tone ▸ Idioms related to quarter tone ▸ Wikipedia articles (New!) ▸ Words that often appear near quarter tone ▸ Rhymes of quarter tone ▸ Invented words related to quarter tone