e·mer·gen·cy / iˈmərjənsē/ • n. (pl. -cies) a serious, unexpected, and often dangerous situation requiring immediate action: your quick response in an emergency could be a lifesaver. ∎ [as adj.] arising from or needed or used in an emergency: an emergency exit. ∎ a person with a medical condition requiring immediate treatment. ∎ short for emergency room: he was rushed into emergency.