jittery

Jittery is an adjective used to describe a state of nervousness or irritability, often accompanied by trembling or restlessness. It can describe physical movement that is unsteady or tremulous, as when someone holds still but their hands shake, or something that moves in quick, irregular bursts.

Common uses include feeling jittery after caffeine, stress, sleep deprivation, or nervous anticipation, and describing a person who seems tense or on edge in their behavior.

Etymology: Derived from jitter, a verb meaning to shake or move unsteadily; the noun jitter refers to minor, rapid variations or tremors. The exact origin is uncertain, but the sense dates to the late 19th or early 20th century.

In technical contexts, jitter refers to small timing variations in a waveform or clock signal; a jittery system exhibits inconsistent timing that can impair performance in networks, audio, or control systems.

In motion or photography, a jittery shot or footage describes unstable framing or motion, often caused by hand-held operation or mechanical shake.

In medical contexts, jitteriness can be a symptom rather than a diagnosis, associated with anxiety, caffeine intoxication, low blood sugar, withdrawal, or stimulant effects.