The Collaborative International Dictionary of English v.0.48:

eyebrow \eye"brow`\, n.
   The brow or hairy arch above the eye. --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

eyebrow
    n 1: the arch of hair above each eye [syn: eyebrow, brow,
         supercilium]