Anything hyperactive is doing more than it should — a hyperactive child bounces off the walls, and a hyperactive gland secretes too much and makes you feel bad.
It's good to be active, but add hyper and it’s not so good anymore. Hyper comes from a Greek word for “too much.” If someone is hyperactive, she might have attention deficit hyperactivity disorder (ADHD). People who suffer from it are hyperactive and can’t concentrate. You could say they’re hyper, which is short for hyperactive, but that’s not very polite. Hyperactive glands produce too many hormones and throw the body out of whack. Hyperactive things need to settle down.