red line

American

noun

Ice Hockey. a line of the color red that is parallel to and equidistant from the goal lines and divides the rink in half.
a limit, point, or boundary beyond which one may not go without incurring negative consequences.

The use of chemical weapons is a red line, which, if crossed, could trigger military action.

red line British

noun

a point beyond which a person or group is not prepared to negotiate

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of red line

First recorded in 1960–65

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.

But his red line converged on the demand for zero nuclear enrichment.

From BBC

OpenAI CEO Sam Altman told employees Thursday that he too was seeking an agreement with the Pentagon that would include red lines similar to Anthropic's, and that he hoped to help broker a resolution.

From Barron's

Altman said in a note to staff that he had the same "red lines" as Anthropic boss Dario Amodei, who has refused to give the Pentagon unfettered access to the firm's AI tools.

From BBC

Employees at Google and OpenAI signed an online petition urging their companies to maintain the same red lines.

From The Wall Street Journal

Those are two red lines that seem rather reasonable, even to Claude.

From Los Angeles Times

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023