I. adverb, adjective 1. on fire; burning[as adj.] • the house was alight when the firemen arrived
• [as adv.]
flammable liquid was set alight.
2. shining brightly[as adj.] • a single lamp was alight
‹figurative› the boy’s face was alight with excitement.
II. phrases set the world alight see set the world on fire at fire.
– origin late Middle English: probably from the phrase on a light (= lighted) fire.