# Trojan horse

idiom · CEFR B1

Source: https://englishreference.com/idiom/trojan-horse
Updated: 2026-07-29

## Meaning

Something that looks like a harmless gift but secretly carries a hidden danger inside.

## Examples

- That free app turned out to be a Trojan horse full of ads.
- Critics warned that the friendly-looking merger was a Trojan horse designed to shut down the smaller company from within.
- The reform was praised as a gift to workers, but union leaders saw a Trojan horse: buried in its final clause was a rule that quietly stripped away their right to strike.

## Origin

For ten long years the Greeks had camped on the plain before Troy, and for ten long years the great walls had held. Spears had shattered against them, heroes had died beneath them, and still the gates stood shut. The Greeks were exhausted, and Troy would not fall to strength alone. So Odysseus thought of a trick. The Greek carpenters felled tall pines and built a horse of wood — vast, hollow, taller than the huts around it — and into its dark belly climbed the bravest of the soldiers, swords drawn, holding their breath in the gloom. At dawn the Trojans woke to an empty shore. The Greek ships were gone, the camp was ash, and there on the sand stood the great horse, gleaming, an offering to the gods. The people threw open their gates and dragged the wonder inside their own walls, singing, garlanded, certain the long war was won. That night, while Troy slept off its feasting, the belly of the horse swung open. The hidden men climbed down, threw wide the gates to the fleet that had only pretended to sail away, and the city that ten years of war could not break fell in a single night of fire. We speak of a Trojan horse whenever something is welcomed in as a gift or a friend, only to loose the very danger it was hiding all along.

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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.