Emily Dickinson Lexicon

DUN, a. [Sax. dunn; W. dwn; Ir. donn; qu. tan, tawny. See Class Dn No. 3, 24, 28, 35.]

1. Of a dark color; of a color partaking of a brown and black; of a dull brown color; swarthy.
2. Dark; gloomy. In the dun air sublime. – Milton.