# guardrail

/ˈɡɑɹˌdɹeɪɫ/ (US) · /ɡˈɑːdɹeɪl/ (UK) · CEFR B2 · Noun

Source: https://englishreference.com/word/guardrail
Updated: 2026-09-18

## Definition

A rule built into an AI system to stop it from doing something harmful or wrong.

For teachers: A technical constraint designed to prevent an AI system from producing unwanted outputs or taking unsafe actions.

## Examples

- Developers added guardrails to limit certain model outputs.
- The system has guardrails that prevent unauthorized actions.

---

From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.