red line

American  

noun

1. Ice Hockey. a line of the color red that is parallel to and equidistant from the goal lines and divides the rink in half.

2. 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.

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red line British  

noun

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

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Etymology

Origin of red line

First recorded in 1960–65

Example Sentences

Yet US interest in the vast Arctic territory has not waned, and the red line on the Greenlandic -- and Danish -- side remains the same: any transfer of sovereignty is off the table.

From Barron's

Anthropic has seen a surge of public goodwill since Chief Executive Dario Amodei said the company wouldn’t compromise its red lines to do a deal.

From The Wall Street Journal

Pahlavi accused them of threatening national unity and said "Iran's territorial integrity is the ultimate red line."

From Barron's

"All the red lines have already been crossed," said Qatar's foreign ministry spokesman Majed al Ansari at a press briefing on Tuesday.

From BBC

A separate statement from worker organizations and unions representing Amazon.com, Google and Microsoft employees urged their own employers to maintain the same red lines in any contracts with the Pentagon.

From The Wall Street Journal