v.intr.
1 a (often foll. by from) descend from a vehicle. b dismount from a horse.
2 descend and settle; come to earth from the air.
3 (foll. by on) find by chance; notice.
Etymology: OE alihtan (as A-(2), lihtan LIGHT(2) v.)
2.
predic.adj.
1 on fire; burning (they set the old shed alight; is the fire still alight?).
2 lighted up; excited (eyes alight with expectation).
Etymology: ME, prob. f. phr. on a light (= lighted) fire
Useful english dictionary. 2012.