noun
1. : space that cannot be reached by fire from a given weapon or a given point — called also dead ground
2. : the portion of the respiratory system which is external to the bronchioles and through which air must pass to reach the bronchioles and alveoli — called also physiologic dead space
3. : a space left in the body as the result of a surgical procedure (as that in the chest following excision of a lung or that in an improperly closed surgical wound)
4. : space (as in a truck or steamer) that is not utilized or occupied