The Collaborative International Dictionary of English v.0.48:

Supercilium \Su`per*cil"i*um\, n. [L.] (Zool.)
   The eyebrow, or the region of the eyebrows.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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