the act of checking a horse quickly with a single strong pull of the reins.
2.
Ophthalmology. the series of small, jerky movements of the eyes when changing focus from one point to another.
Origin: 1720–30; < Frenchsaccade jerk, jolt, orig., movement of a horseman who abruptly pulls the reins, equivalent to Middle Frenchsaqu(er) to pull violently (N dialectal variant of Old Frenchsachier, ultimately derivative of sacsack1, hence presumably with sense “withdraw from a sack”) + -ade-ade1
saccade sac·cade (sā-käd', sə-) n. A rapid intermittent eye movement, as that which occurs when the eyes fix on one point after another in the visual field.