Definition of "lucid"

[T]he book, constructed in short, lucid episodes, can be satisfyingly read as a sequence of provocative talks, at once well informed and vatic.

2014 September 26, Tom Payne, “Sapiens: a Brief History of Humankind by Yuval Noah Harari, review: 'urgent questions' ”, in The Daily Telegraph (Review)‎

The atmosphere was unusually clear, as if loath to part with the daylight; but the moon, like a round of lucid snow, had risen on the sky; and a pale, soft gleam, came from the lamps amid the foliage.

1837, L[etitia] E[lizabeth] L[andon], “The Fête”, in Ethel Churchill: Or, The Two Brides. […], volume III, London: Henry Colburn, […], page 57

The day before nightmare-initiated lucids, subjects reported more depressed feelings […]

1986, Benjamin B. Wolman, Montague Ullman, Handbook of states of consciousness, page 163