Meaning
A Trojan horse / A gift that brings trouble
Example
Foi presente de grego, parece que seu melhor amigo deu um chocolate envenenado a ele.
It was a Trojan horse, his best friend gave him poisoned chocolate.
Origin
A 'Greek gift' is the Trojan Horse. In Virgil's Aeneid (Book II) the priest Laocoön warns the Trojans timeo Danaos et dona ferentes — 'I fear the Greeks even when they bring gifts.' The wooden horse hid Greek soldiers and led to the sack of Troy.
Source: Britannica — Trojan horse.
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More idioms
Acertar na moscaTo guess correctly / To hit the nail on the headAmigo da onçaA fake/false friendAndar na linhaTo toe the line / To behave properlyArmar um barracoTo cause a public sceneRodar a baianaTo cause a public scene / To go ballisticArrumar sarna pra se coçarTo ask for troubleArrastar as asasTo hit on someone / To flirtAbrir o jogoTo come clean / To open upArregaçar as mangasTo roll up one's sleeves / To get to workAgarrar com unhas e dentesTo hold on for dear life / To seize an opportunity