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Any of several large sea ducks, especially of the genus Somateria of northern regions, having soft, commercially valuable down and predominantly black and white plumage in the male.
[Back-formation from eiderdown.]
(Animals) any of several sea ducks of the genus Somateria, esp S. mollissima, and related genera, which occur in the N hemisphere. The male has black and white plumage, and the female is the source of eiderdown
[C18: from Old Norse æthr; related to Swedish ejder, Dutch, German Eider]
any of several large diving ducks, esp. of the genus Somateria, of northern seas.