Main Entry:

ei·der

Pronunciation:

\ˈī-dər\

Function:

noun

Etymology:

Dutch, German, or Swedish, from Icelandic æthur, from Old Norse æthr

Date:

1743

1 : any of several large northern sea ducks (genera Somateria and Polystica) having fine soft down that is used by the female for lining the nest —called also eider duck 2 : eiderdown 1