What is the meaning of light up?

verb

• Start to burn with a bright flame.
  • usage: "The coal in the BBQ grill finally lit up"
• Make lighter or brighter.
  • usage: "This lamp lightens the room a bit"
  • synonyms: light, illume, illumine, illuminate
• Become clear.
  • usage: "The sky cleared after the storm"
  • synonyms: clear up, clear, brighten
• Ignite.
  • usage: "The sky lit up quickly above the raging volcano"
• Begin to smoke.
  • usage: "After the meal, some of the diners lit up"
  • synonyms: fire up, light