Webster's Revised Unabridged Dictionary · 1913

Dun

Dun (dun) , noun

[See Dune.]

A mound or small hill.

Dun , transitive verb

To cure, as codfish, in a particular manner, by laying them, after salting, in a pile in a dark place, covered with salt grass or some like substance.

Dun (dun) , verb, transitive and intransitive

[Anglo-Saxon dyne noise, dynian to make a noise, or from Icelandic dynr, duna, noise, thunder, duna to thunder; the same word as English din. r74. See Din.]

To ask or beset (for example, a debtor), for payment; to urge importunately.
Hath she sent so soon to dun? — Swift

Dun , noun

1.
One who duns; a dunner.
To be pulled by the sleeve by some rascally dun. — Arbuthnot
2.
An urgent request or demand of payment; as, he sent his debtor a dun.

Dun , adjective

[Anglo-Saxon dunn, of Celtic origin; compare Welsh 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
Collocations (2)
Dun crow (Zoology) , the hooded crow; -- so called from its color; -- also called hoody, and hoddy.
Dun diver (Zoology) , the goosander or merganser.