What is a ball of rats called? - briefly
A group of rats is commonly referred to as a swarm. The alternative collective noun pack is also used, but “swarm” is the standard term.
What is a ball of rats called? - in detail
A tight grouping of rodents is commonly referred to as a “rat ball.” The expression appears in wildlife literature and informal reports when several individuals huddle together, typically for warmth or protection. The phrase functions as a collective noun, similar to “herd of deer” or “flock of birds,” and is used without modifiers such as “large” or “massive,” which would add unnecessary evaluation.
The term’s origin lies in the visual similarity between a compact mass of rats and a spherical object. Early naturalists employed the word to describe colonies observed in sewers or abandoned structures, noting that the animals often curl into a roughly spherical shape when threatened. Contemporary usage is found in pest‑control documentation, where “rat ball” designates a cluster that may require special handling, and in media accounts of infestations.
When precise language is required, professionals may prefer “rat colony” or “rat nest” to indicate a permanent, breeding population. “Rat swarm” sometimes describes a transient surge of individuals moving together, especially during foraging. However, the specific phrase that directly answers the query remains “rat ball.”