The Collaborative International Dictionary of English v.0.48:

eyebrow pencil \eye"brow pen"cil\ ([imac]"brou p[e^]n"s[i^]l),
   n.
   a cosmetic pencil-like device used to apply a tint to the
   eyebrows, or darken lighter areas on the eyebrows. It is
   sometimes used to create a "beauty mark" on the face.
   [PJC]

WordNet (r) 3.0 (2006):

eyebrow pencil
    n 1: makeup provided by a cosmetic pencil that is used to darken
         the eyebrows