1. A condition characterized by excessive restlessness and movement: Some students in school have a problem of hyperactivity in that they cannot sit still and seem to be quite nervous, uneasy, jittery, and therefore disrupt the lessons and concentration of the other students.
2. A higher than normal level of activity: Susan showed a high degree of hyperactivity at the dinner table that evening with an excessive amount of talking and fidgeting.

A body organ can be described as hyperactive if it is more active than normal and a person's behavior can also be considered as hyperactive.

People who are affected by hyperactivity always seem to be in motion. They can't sit still. They may dash around or talk incessantly. Sitting still through a lesson can be an impossible task. They may roam around the room, squirm in their seats, wiggle their feet, touch everything, or noisily tap a pencil. They may also feel intensely restless.

Random excess motion and exertion that fulfills no intention: In an organic brain disease, stimulation sufficient to produce any response typically provokes purposeless hyperactivity in addition to the appropriate response.