/ Dictionary / Index E eider: Meaning and Definition of Find definitions for: ei•der Pronunciation: (ī'dur), [key] — n. See eiderdown. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: eider (Thesaurus) eicosapentaenoic acid eiderdown Related Content Daily Word Quiz: neologism Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language