a cautionary sign of danger
the signal to stop
- At night, ships at sea carry a red light on the port side and a green light on the starboard.
- A red light is usually a signal of danger.
- He drove through a red light (ie passed it without stopping) and a policeman saw him.
- He was such an impatient driver (=He was so impatient a driver) that he went through the red light.