Which of the following terms describes a legal act preventing someone from performing a specific action?

The term that accurately describes a legal act that prevents someone from performing a specific action is "injunction." An injunction is a court order that compels a party to do, or refrain from doing, certain acts. It can be temporary or permanent, and is often sought in situations where a party believes that they will suffer irreparable harm without the court's intervention.

Injunctions are commonly used in various legal contexts, such as in cases involving property disputes, contract enforcement, or matters related to non-compete clauses. They serve as a powerful tool for the court to intervene and protect rights before a full trial can occur, making them essential for maintaining the status quo and preventing harm.

The other options, while they may overlap in meaning in certain legal contexts, do not specifically encompass the definition of preventing action in the same precise way as an injunction. A mandate usually refers to a command or indication to carry out an action, a restriction implies limitations but may not involve legal authority, and an order can be broad and not necessarily tied to an act of prevention.