A startled, fearful or defensive feline may strike the pose of the classic Halloween cat to make itself look larger and more threatening. It turns to one side with back arched, hackles raised, ears turned back and teeth bared. Sensing a potential threat, a cat tenses its body, lowers its tail and raises the fur on its back and tail. On its toes, it is ready to flee the instant the need arises. If it is preparing to attack, the cat will crouch or lie on its side or back, narrow its eyes to focus on its target, hiss and bare its teeth and claws. A feline that takes this posture isn't interested in your affection; it means business. You're best to stay out of the way.
