Lightness rhymes with:
politeness, brightness, forthrightness, politeness, rightness, tightness, whiteness, abruptness, absoluteness, acuteness, alertness, appropriateness, astuteness, bluntness, brightness, compactness, completeness, correctness, cuteness, directness, earnestness, eyewitness, faintness, fastness, fitness, flatness, forthrightness, gauntness, greatness, hartness, inertness, jointness, lateness, lightfastness, neatness, politeness, quietness, remoteness, rightness, robustness, separateness, shortness, softness, steadfastness, stoutness, sweetness, swiftness, tartness, tightness, unpleasantness, vastness, wetness, whiteness, witness, witness'
Lightness sounds like:
lactating, lasting, legitimacy, legitimize, legitimizes, lightening, lightens, lightheadedness, lighting, lighting's, lightning, lightnings, liquidating, liquidations, listening, listens, listing, listings, locating, locations, lusitania's, lusitanias, lusting