A group of rats is called a mischief or a horde. However, there are other terms that can also be used to describe a group of rats, such as a pack, a swarm, or a colony. The exact term used to describe a group of rats can vary depending on the context and the speaker's preference. Rats are highly social animals that are known for their ability to form large, complex communities with hierarchies and social structures. They are found throughout the world and are often considered pests because of their ability to spread disease and cause damage to property.