#1 light up v. start to burn with a bright flame; "The coal in the BBQ grill finally lit up". wn #2 light up v. make lighter or brighter; "This lamp lightens the room a bit". wn #3 light up v. become clear; "The sky cleared after the storm". wn #4 light up v. ignite; "The sky lit up quickly above the raging volcano". wn #5 light up v. begin to smoke; "After the meal, some of the diners lit up". wn