'D-layer' definitions:

Definition of 'D-layer'

From: WordNet
noun
The lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves [syn: D-layer, D region]

Definition of 'D-layer'

From: GCIDE
  • D-layer \D-layer\ n. the lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves.
  • Syn: D region. [WordNet 1.5]