civil defense (US) or Brit civil defence noun
[noncount] : a group of people who are not part of the military but are trained to protect and help people if an enemy attacks their country or if there is a natural disaster (such as a flood or earthquake)
▪ She's in training to be part of the local civil defense. ▪ the head of civil defense
▪ She's in training to be part of the local civil defense. ▪ the head of civil defense
