Somnambulism refers to sleepwalking.
Sleepwalking occurs most frequently in children, particularly boys. Sedatives tend to exacerbate rather than cure sleepwalking. The best measures are preventative that is to ensure that the sleepwalker is in a safe room for walking, and cannot accidentally fall through an open window or down stairs. Some types of sleepwalking are related to seizure disorders, bipolar disorders, or other neurological conditions, but most cases are transitory and due to unknown causes.
Other /More definition:
somnambulism refers to repeated sleepwalking that occurs during non-rapid eye movement sleep and so is not the acting out of a dream. The person is difficult to waken and does not recall the experience.