d region dreggy • dregless · · · Info · Definitions · Characters · · d region · · Text Common · · Latin · · Scripts 8 · · Length 3 · · Syllables Definitions · · · (noun) the lowest region of the ionosphere (35 to 50 miles up) that reflects low-frequency radio waves. Synonyms: D-layer, D region. · · Noun Definition 1 Characters · · space U+0020 d latin small letter d U+0064 e latin small letter e U+0065 g latin small letter g U+0067 i latin small letter i U+0069 n latin small letter n U+006E o latin small letter o U+006F r latin small letter r U+0072