v.1. To illuminate or be illuminated: All the neon signs along the street light up at night.
2. To cause something to illuminate or be illuminated: The morning sun lit up the room. The miners lit their headlamps up and descended into the shaft.
3. To begin to burn: The gas burners lit up on the first try.
4. To cause something to burn; ignite something: I lit up a match and started the fire. I'll get some wood and light a fire up.
5. To ignite and begin smoking something, especially a cigarette, cigar, or pipe: I went out to the porch and lit up a cigar. He lit his pipe up with a match. She took a cigarette from the case and lit up.
6. To become animated or cheerful: The children's eyes lit up when they saw the size of the cake.
7. To cause someone or something to become animated or cheerful: The presence of the movie star lit up the room. He was feeling sad, but the surprise party lit his face up.