saccade

n. rapid irregular movement of the eye; quick and strong checking of a horse by pulling the reins

For the anti-ship missile, see C-802. A saccade is a fast movement of an eye, head or other part of an animal's body or device. It can also be a fast shift in frequency of an emitted signal or other quick change. However, this article deals with saccadic eye motion. With respect to the eye, saccades are quick, simultaneous movements of both eyes in the same direction. Initiated by the frontal lobe of the brain (Brodmann area 8), saccades serve as a mechanism for fixation, rapid eye movement and the fast phase of optokinetic nystagmus. The word appears to have been coined in the 1880s by French ophthalmologist E Javal, who used a mirror on one side of a page to observe eye movement in silent reading, and found that it involves a succession of discontinuous individual movements.
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Saccade /sac·cade/ [Fr.] the series of involuntary, abrupt, rapid, small movements or jerks of both eyes simultaneously in changing the point of [more]Saccade - Community and Resources

n. jolt, jerk, backlash, twitch

adj. jerky, tending to move in fits and starts

(n.)
A sudden, violent check of a horse by drawing or twitching the reins on a sudden and with one pull.