We found 15 dictionaries that define the word principal axis:

General (11 matching dictionaries)

1. principal axis: Oxford Learner's Dictionaries
2. principal axis: Collins English Dictionary
3. principal axis: Vocabulary.com
4. principal axis: Wordnik
5. principal axis: Infoplease Dictionary
6. principal axis: Dictionary.com
7. Principal axis (crystallography), Principal axis (mechanics), Principal axis: Wikipedia, the Free Encyclopedia
8. principal axis: Rhymezone
9. principal axis: FreeDictionary.org
10. principal axis: Mnemonic Dictionary
11. principal axis: TheFreeDictionary.com

Computing (1 matching dictionary)

12. principal axis: Encyclopedia

Medicine (2 matching dictionaries)

13. principal axis: Merriam-Webster Medical Dictionary
14. online medical dictionary (No longer online)

Tech (1 matching dictionary)

15. Schlumberger Oilfield Glossary (No longer online)

Definitions from WordNet (principal axis) ▸ noun:  a line that passes through the center of curvature of a lens so that light is neither reflected nor refracted Phrases: principal optic axis, Principal axis theorem, more... ▸ Words similar to principal axis ▸ Usage examples for principal axis ▸ Idioms related to principal axis ▸ Wikipedia articles (New!) ▸ Words that often appear near principal axis ▸ Rhymes of principal axis ▸ Invented words related to principal axis