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• red light
  red light

  noun

  a red lamp, used as a traffic signal to mean “stop.”
• red-light
  red-light

  verb (used with object)

  to stop or deter by means of or as if with a red light.

red light

¹ American  

noun

red lights plural

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.

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red-light ² American  

[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.

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red light British  

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

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Other Word Forms

Noun Inflected Forms

• red lights
  plural

Etymology

Origin of red light¹

First recorded in 1840–50

Origin of red-light²

First recorded in 1895–1900

Example Sentences

The red light and a siren from a cop.

From Salon • Jul. 3, 2026

Investors were surprised by the timing of the shake-up and are viewing it as a flashing red light, fearing Jordan will scrap long-term growth targets.

From The Wall Street Journal • Jun. 25, 2026

When these particles collide with oxygen atoms high in the atmosphere, the atoms release energy as soft red light, producing rare auroras visible from the ground.

From Science Daily • May 22, 2026

On the same floor, a neon bed is bathed in red light.

From Los Angeles Times • May 20, 2026

Percy’s face was hard to read in the dim red light.

From "The House of Hades" by Rick Riordan

Related Words

• traffic signal