eiderdown         
noun uk/ˈaɪ.də.daʊn/ us/ˈaɪ.dɚ.daʊn/ (US comforter)
 [ C ]鸭绒垫,鸭绒被 
a thick covering for the top of a bed, filled with soft feathers or warm material
  She snuggled beneath the eiderdown. 她舒适地蜷伏在鸭绒被下面。 
 Compare: duvet
  [ U ]鸭绒 
the soft feathers of a duck, used for filling pillows, bed covers, etc.