Dun \Dun\, a. [AS. dunn. of Celtic origin; cf. W. dwn, Ir. & Gael. donn.] Of a dark color; of a color partaking of a brown and black; of a dull brown color; swarthy. Summer's dun cloud comes thundering up. -- Pierpont. Chill and dun Falls on the moor the brief November day. --Keble. {Dun crow} (Zo["o]l.), the hooded crow; -- so called from its color; -- also called {hoody}, and {hoddy}. {Dun diver} (Zo["o]l.), the goosander or merganser.