The Collaborative International Dictionary of English v.0.48:

White-face \White"-face`\, n.
   A white mark in the forehead of a horse, descending almost to
   the nose; -- called also white-blaze.
   [1913 Webster]

WordNet (r) 3.0 (2006):

whiteface
    n 1: hardy English breed of dairy cattle raised extensively in
         United States [syn: Hereford, whiteface]
    2: a clown whose face is covered with white make-up