Lucid, a.
Etymology: [L. lucidus, fr. lux, lucis, light. See Light, n.]
1. Shining; bright; resplendent; as, the lucid orbs of heaven. Lucid, like a glowworm. Sir I. Newton. A court compact of lucid marbles. Tennyson.
2. Clear; transparent. " Lucid streams." Milton.
3. Presenting a clear view; easily understood; clear. A lucid and interesting abstract of the debate. Macaulay.
4. Bright with the radiance of intellect; not darkened or confused by delirium or madness; marked by the regular operations of reason; as, a lucid interval.
1 more senses
Syn. -- Luminous; bright; clear; transparent; sane; reasonable. See Luminous.
Shades of meaning
Fernald has no entry of its own for lucid; he lists it under clear.
Where he writes about it:
Lucid and pellucid refer to a shining clearness, as of crystal. — from clear