red light
1 Americannoun
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a red lamp, used as a traffic signal to mean “stop.”
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an order or directive to halt an action, project, etc..
There's a red light on all unnecessary expenses.
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a children's running game in which players must stop when “Red light!” is called.
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a signal of danger; warning.
verb (used with object)
noun
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a signal to stop, esp a red traffic signal in a system of traffic lights
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a danger signal
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an instruction to stop or discontinue
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a red lamp in a window of or outside a house indicating that it is a brothel
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( as modifier )
a red-light district
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Etymology
Origin of red light1
First recorded in 1840–50
Origin of red-light2
First recorded in 1895–1900
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
"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
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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.