1. Introduce light into
   "The morning sun lit up the room";
   - light, illume [archaic], illumine, illuminate
    
2. Start to burn with a bright flame
   "The coal in the BBQ grill finally lit up"
    
3. Ignite
   "The sky lit up quickly above the raging volcano"
    
4. Become free from clouds or less cloudy; become brighter
   "The sky lit up after the storm";
   - clear up, clear, brighten
    
5. Begin to smoke
   "After the meal, some of the diners lit up";
   - fire up, light

Derived forms: lights up, lit up, lighting up

Type of: alter, catch fire, change, combust, conflagrate, erupt, ignite, light, lighten, lighten up, take fire, vary

Antonym: cloud