WordNet (r) 3.0 (2006):

light up
    v 1: start to burn with a bright flame; "The coal in the BBQ
         grill finally lit up"
    2: make lighter or brighter; "This lamp lightens the room a bit"
       [syn: light, illume, illumine, light up,
       illuminate]
    3: become clear; "The sky cleared after the storm" [syn: clear
       up, clear, light up, brighten] [ant: cloud,
       overcast]
    4: ignite; "The sky lit up quickly above the raging volcano"
    5: begin to smoke; "After the meal, some of the diners lit up"
       [syn: light up, fire up, light]

Moby Thesaurus II by Grady Ward, 1.0:

93 Moby Thesaurus words for "light up":
   annoy, arouse, awake, awaken, bank, beacon, blow the coals,
   blow up, brace up, brighten, brighten up, buck up, burn,
   call forth, call up, cheer up, chirk up, conflagrate, enkindle,
   enlighten, enrage, excite, fan, fan the fire, fan the flame, feed,
   feed the fire, fire, flame, flood with light, floodlight, foment,
   frenzy, heat, highlight, ignite, illume, illuminate, illumine,
   impassion, incense, incite, inflame, infuriate, irradiate, key up,
   kindle, lather up, light, light the fuse, lighten, luminate,
   madden, move, overexcite, overshine, perk up, rekindle, relight,
   relume, relumine, revive, rouse, set astir, set fire to,
   set on fire, shed light upon, shine upon, spotlight, steam up,
   stir, stir the blood, stir the embers, stir the feelings,
   stir the fire, stir up, stoke, stoke the fire, strike a light,
   summon up, take heart, throw light upon, torch, touch off, turn on,
   wake, wake up, waken, warm, warm the blood, whip up, work into,
   work up