Synonyms for Lucid:

adj.

all (adjective)
crystal clear, limpid, luculent, pellucid, perspicuous.
articulate (adjective)
articulate, clear, coherent, direct, eloquent, expressive, fluent, glib, intelligible, loquacious, smooth, succinct, well-spoken.
bright (adjective)
beaming, blazing, blinding, bright, brilliant, dazzling, fiery, flaring, flashing, fluorescent, garish, glaring, gleaming, glinting, glistening, glittering, glowing, illuminating, incandescent, luminescent, luminous, lurid, lustrous, neon, phosphorescent, radiant, radiating, scintillating, shimmering, shining, sparkling, vivid, well lit, resplendent.
clear (adjective)
legible, lucent, perspicuous, simple, straightforward.
coherent (adjective)
articulate, consistent, logical.
compos mentis (adjective)
well-balanced.
intelligible (adjective)
coherent, comprehensible, consistent, crisp, decipherable, legible, perspicuous, plain, self-explanatory, straightforward, understandable, clear, direct, intelligible.
lucid (adjective)
beaming, bright, clear, comprehensible, crystal clear, crystalline, diaphanous, glassy, gleaming, incandescent, intelligible, limpid, luminous, lustrous, normal, pellucid, plain, radiant, rational, reasonable, resplendent, sane, translucent, transparent, understandable.
sane (adjective)
balanced, down-to-earth, normal, rational, realistic, reasonable, sane, sensible, well-balanced, Sober-minded.
transparent (adjective)
crystalline, diaphanous, filmy, glassy, limpid, lucent, revealing, translucent, transparent, clear.

n.

alert, clearly, thinking, well-adjusted, wide-awake, with-it. easy, make sense, simple, Compos-mentis. touch. lucid (noun)
clear, coherent, crystal clear, crystalline, limpid, logical, luculent, pellucid, perspicuous, rational, sane, transparent.

Other synonyms:

thinking, well-adjusted, Compos-mentis. clearly. alert. Other relevant words:
alert, clearly, crystal clear, easy, logical, luculent, pellucid, resplendent, simple, thinking, touch, well-adjusted, with-it.

Usage examples for lucid

  1. But on one point at least it remained alert and lucid he still could think out his course clearly. – Christopher Columbus by Mildred Stapley
  2. The most lucid arguments and the most earnest remonstrances were all in vain. – The Rise of the Dutch Republic, Volume II.(of III) 1566-74 by John Lothrop Motley Last Updated: January 25, 2009
  3. He looked her in the starry, lucid eyes, where a divine fervour deepened. – Indian Summer by William D. Howells