In biology, the term kinesis means movement, especially the kind that's caused by a stimulus. If you turn on the kitchen light at night and see cockroaches scatter, they are showing kinesis.
The word kinesis comes up in biology class, especially if you're studying the behavior of animals. When animals are affected by a stimulus — like light, sound, or physical touch — and react by moving, that's kinesis. One distinguishing trait of kinesis is that the movement it causes is random, not directly connected to the stimulus. The word kinesis is Greek, meaning simply "movement or motion."