Jittery can describe jerky or nervous actions. If you consume a lot of caffeine, you might appear jittery.
If a running back is darting around quickly and unpredictably, making herky-jerky movements, he's jittery. Also, jittery applies to people who feel nervous or tense. If you're worried about a test, you'll feel jittery. During the last minute of a basketball game, some players get jittery. Synonyms for this nervous kind of jittery are edgy, high-strung, jumpy, nervy, and uptight.