red light

¹ American  

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.

---

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.

---

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

---

Etymology

Origin of red light¹

First recorded in 1840–50

Origin of red-light²

First recorded in 1895–1900

Example Sentences

"Dragonflies can likely see deeper into red light than most insects."

From Science Daily • Apr. 9, 2026

We’re mostly side by side, but I tend to drift in front of her, especially if one of us is on the phone, or we’re trying to beat a crosswalk red light.

From The Wall Street Journal • Apr. 9, 2026

It was cold—the temperature settled in at 30 degrees—and blue and red light flashed on the wall of Quirky Books from a nearby surveillance tower installed by the police.

From Slate • Mar. 25, 2026

For investors, Wall Street’s optimism is a flashing red light, notes DataTrek co-founder Nicholas Colas, who flagged the FactSet report in his newsletter Monday, calling it, “the most disturbing graph we saw this entire weekend.”

From Barron's • Mar. 24, 2026

The red light was dying out fast from the hills and from the windy sea.

From "A Wizard of Earthsea" by Ursula K. Le Guin

Related Words

• traffic signal