guardrail

American  

[gahrd-reyl] / ˈgɑrdˌreɪl /

noun

1. Also guardrailing. a protective railing, as along a road or stairway.

2. Railroads. a rail laid parallel to a track to prevent derailment or to keep derailed rolling stock from leaving the roadbed.

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guardrail British  

/ ˈɡɑːdˌreɪl /

noun

1. a railing at the side of a staircase, road, etc, as a safety barrier

2. Also called (Brit): checkrail.  railways a short metal rail fitted to the inside of the main rail to provide additional support in keeping a train's wheels on the track

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Etymology

Origin of guardrail

First recorded in 1825–35; guard + rail ¹

Explanation

A guardrail is a strong fence at the side of the road that can help protect drivers from serious injury. On a highway, center guardrails make it easier to avoid colliding with a car going the opposite direction. Guardrails protect cars from hitting large roadside objects like trees and signs, or from hazards such as steep hills beside the highway. Additionally, guardrails are designed to keep cars upright, even when they strike the rail at fairly high speeds. In some places, low, protective fences around public spaces are also called guardrails — in this case, they're guarding against pedestrian injuries. "Stay back from the guardrail around the lion enclosure!"

Example Sentences

When AI systems are manipulated into performing malicious actions, critical details must be shared: attack vectors, guardrail failures, and forensic signatures that might help others detect similar intrusions.

From The Wall Street Journal • Nov. 23, 2025

The project also includes restoring and replacing two overhead sign structures, doing 98 sign panel replacements, upgrading 6,400 feet of guardrail and upgrading 10 curb ramps.

From Los Angeles Times • Aug. 25, 2025

He said his time in prison helped him develop a "moral guardrail".

From BBC • Aug. 21, 2025

Stolle compared the rise of EVs with the 1990s, when the popularity of SUVs and pickup trucks compelled a nationwide changing of the guardrail, toward a design known as the Midwest Guardrail System.

From Slate • Jan. 7, 2025

And the guardrail made of pipe—the one attached to the right side of the porch stairs.

From "The Running Dream" by Wendelin Van Draanen