The Collaborative International Dictionary of English v.0.48:

highlight \highlight\ v. t.
   1. To emphasize or call attention to, by moving into the
      foreground or otherwise making more prominent.

   Syn: foreground, spotlight, play up.
        [WordNet 1.5]

   2. To make (part of a text or image) more prominent,
      especially by making it of a lighter hue or of a different
      color than the remaining part.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

highlight \highlight\ n.
   The part of an image that has the most intense light.
   [PJC]

   2. The most memorable or enjoyable part; -- of events or
      activities; as, the highlight of our trip was the tour of
      the Vatican.
      [PJC]

WordNet (r) 3.0 (2006):

highlight
    n 1: the most interesting or memorable part; "the highlight of
         the tour was our visit to the Vatican" [syn: highlight,
         high spot]
    2: an area of lightness in a picture [syn: highlight,
       highlighting]
    v 1: move into the foreground to make more visible or prominent;
         "The introduction highlighted the speaker's distinguished
         career in linguistics" [syn: foreground, highlight,
         spotlight, play up] [ant: background, downplay,
         play down]
    2: apply a highlighter to one's cheeks or eyebrows in order to
       make them more prominent; "highlight the area above your
       eyebrows"

Moby Thesaurus II by Grady Ward, 1.0:

151 Moby Thesaurus words for "highlight":
   accent, accentuate, affect, arc lighting, argue, be indicative of,
   be significant of, be symptomatic of, beacon, belabor, bespeak,
   betoken, black and white, brandish, breathe, brighten, brighten up,
   bring forth, bring forward, bring into view, bring out,
   bring to notice, characterize, chiaroscuro, connote, contrast,
   dangle, decorative lighting, demonstrate, denominate, denote,
   develop, differentiate, direct lighting, disclose, display,
   divulge, dramatize, dwell on, electric lighting, emanation, embody,
   emphasize, enact, enlighten, enlightenment, entail, evidence,
   evince, exhibit, expose to view, express, feature,
   festoon lighting, flaunt, flood with light, floodlight,
   floodlighting, flourish, fluorescent lighting, gaslighting,
   give emphasis to, give evidence, give sign, give token,
   glow lighting, harp on, high spot, highlights, hint, identify,
   illume, illuminate, illumination, illumine, incandescent lighting,
   incarnate, indicate, indirect lighting, involve, irradiance,
   irradiancy, irradiate, irradiation, italicize, light,
   light and shade, light source, light up, lighten, lighting,
   luminate, luminous energy, make clear, make plain, manifest, mark,
   materialize, mean, note, outstanding feature, overaccentuate,
   overemphasize, overhead lighting, overshine, overstress, parade,
   perform, photosensitivity, place emphasis on, point up, present,
   produce, punctuate, radiance, radiancy, radiant energy, radiation,
   relume, relumine, represent, reveal, roll out, rub in, set forth,
   shed light upon, shine upon, show, show forth, sidelight, signify,
   spot lighting, spotlight, stage lighting, stand for, star, stress,
   strip lighting, suggest, symptomatize, symptomize, testify,
   throw light upon, token, tonality, trot out, underline, underscore,
   unfold, visible radiation, wave