Quickness, n.
1. The condition or quality of being quick or living; life. [Obs.] Touch it with thy celestial quickness. Herbert.
2. Activity; briskness; especially, rapidity of motion; speed; celerity; as, quickness of wit. This deed . . . must send thee hence With fiery quickness. Shak. His mind had, indeed, great quickness and vigor. Macaulay.
3. Acuteness of perception; keen sensibility. Would not quickness of sensation be an inconvenience to an animal that must lie still Locke
4. Sharpness; pungency of taste. Mortimer.
1 more senses
Syn. -- Velocity; celerity; rapidity; speed; haste; expedition; promptness; dispatch; swiftness; nimbleness; fleetness; agility; briskness; liveliness; readiness; sagacity; shrewdness; shrewdness; sharpness; keenness.
Shades of meaning
Fernald lists quickness only as an antonym, under stupidity.
He lists it without comment; the entries above explain its neighbors.