WordReference Random House Unabridged Dictionary of American English © 2026
D region, 
  1. Aerospace, Physicsthe lowest region of the ionosphere, in which the D layer develops.
  • 1925–30

Collins Concise English Dictionary © HarperCollins Publishers::
D region, D layer
  1. the lowest region of the ionosphere, extending from a height of about 60 kilometres to about 90 kilometres: contains a low concentration of free electrons and reflects low-frequency radio waves
    See also ionosphere
'D region' also found in these entries (note: many are not synonyms or translations):
D layer - ionosphere

Forum discussions with the word(s) "D region" in the title:


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