The Collaborative International Dictionary
Eider \Ei"der\, n. [Of Scand. origin, cf. Icel [ae]?r; akin to Sw. eider, Dan. ederfugl.] (Zo["o]l.) Any species of sea duck of the genus Somateria, esp. Somateria mollissima, which breeds in the northern parts of Europe and America, and lines its nest with fine down (taken from its own body) which is an article of commerce; -- called also eider duck. The American eider ( S. Dresseri), the king eider ( S. spectabilis), and the spectacled eider ( Arctonetta Fischeri) are related species.
Eider down. [Cf. Icel. [ae][eth]ard[=u]n, Sw. eiderd[=u]n, Dan. ederduun.] Down of the eider duck, much sought after as an article of luxury.
Usage examples of "eider down".
The landlord was near spraining his wrist, and I told him for heaven's sake to quit--the bed was soft enough to suit me, and I did not know how all the planing in the world could make eider down of a pine plank.