A berserker cat was a feline known for its courage.
In 2373, Jadzia Dax referred to Worf as having the qualities of a berserker cat, and the heart of a poet. (DS9: "Let He Who Is Without Sin...")
According to the RPG sourcebook Creatures, berserker cats live in the jungles of Errikang VII. They are two meters long, have mottled green-and-brown fur, oversized nostrils and unblinking eyes that can see into the infrared spectrum. Berserker cats are solitary predators that hunt by ambushing vruedebeasts and other grazing animals. These animals are a hazard for archeologists studying the ruins of Errikang VII and wealthy off-worlders sometimes hunt them for sport. Attempts to domesticate them have failed.