The term for a cat with a genetic mutation that causes it to have no tail is called a "Manx" cat. This breed originated on the Isle of Man and is well-known for its unique appearance, characterized by its rounded body and lack of a tail or a very short tail, known as a "rumpy" or "stumpy," respectively. The Manx's trait is due to a dominant gene, adding to its distinctive charm. These cats are known for their playful and friendly personalities, making them popular as pets. The lack of a tail does not affect their physical activity or agility.