red light

noun
1.
a red lamp, used as a traffic signal to mean “stop.”.
2.
an order or directive to halt an action, project, etc.:
There's a red light on all unnecessary expenses.
3.
a children's running game in which players must stop when “Red light!” is called.
4.
a signal of danger; warning.
Origin
1840-50

red-light

[red-lahyt] /ˈrɛdˈlaɪt/
verb (used with object), red-lighted, red-lighting.
1.
Informal. to stop or deter by means of or as if with a red light.
Origin
1895-1900
Examples from the web for red light
  • Printer then flashes red light, demanding new cartridge.
  • He could stay in the fort, the red blanket casting a red light on everything inside.
  • Or maybe you've stopped next to them at a red light and they're checking emails.
  • The next time the red light of violence shone out it seemed of no importance, an irrelevant horror.
  • Then he was struck while walking across an avenue by a car running a red light.
  • When this current returns to the box, it's amplified and used to turn a red light-emitting diode on and off.
  • Light emitted by oxygen is shown as blue, hydrogen emission is shown as green, and nitrogen emission as red light.
  • It uses far red light that's invisible to the animals.
  • If you look closely beyond the bridge, you will see a red light.
  • On city streets, it's legal to right at a red light after stopping.
British Dictionary definitions for red light

red light

noun
1.
a signal to stop, esp a red traffic signal in a system of traffic lights
2.
a danger signal
3.
an instruction to stop or discontinue
4.
  1. a red lamp in a window of or outside a house indicating that it is a brothel
  2. (as modifier): a red-light district