a red sector on a gauge or dial corresponding to conditions that exceed safety limits:ozone readings edged into the red zone
a region that is dangerous or forbidden, or in which a particular activity is prohibited:any officer who parks in the red zone outside the courthouse could receive a ticket
American Football the region between the opposing team’s 20-yard line and goal line, which is a major focus of their attack strategy.
red zone in other Oxford dictionaries
Definition of red zone in the US English dictionary
