We found 17 dictionaries that define the word d region:

General (13 matching dictionaries)

1. D region: Merriam-Webster
2. D region: American Heritage Dictionary of the English Language
3. D region: Collins English Dictionary
4. D region: Vocabulary.com
5. D region: Infoplease Dictionary
6. D region: Dictionary.com
7. D region: Wikipedia, the Free Encyclopedia
8. D region: Rhymezone
9. d region: FreeDictionary.org
10. d region: Mnemonic Dictionary
11. D region: TheFreeDictionary.com
12. D region: Merriam-Webster
13. D region: Wiktionary

Computing (1 matching dictionary)

14. D region: Encyclopedia

Tech (3 matching dictionaries)

15. Glossary of Meteorology (No longer online)
16. National Weather Service Glossary (No longer online)
17. SOLAR-TERRESTRIAL TERMS (No longer online)

(Note: See d_regions as well.)

Definitions from Wiktionary (D region) ▸ noun:  The innermost layer of the ionosphere, located 48 km (30 mi) to 90 km (56 mi) above the surface of the Earth. Opposite: Auroral zone, E region, F region, ionosphere ▸ Words similar to d region ▸ Usage examples for d region ▸ Idioms related to d region ▸ Wikipedia articles (New!) ▸ Words that often appear near d region ▸ Rhymes of d region ▸ Invented words related to d region