Cats hiss at other cats for various reasons, and it can mean anything from a warning shot for other cats to a sign of pain, stress, anxiety, or annoyance. Here are some reasons why cats hiss at each other:

• Warning shots: Hissing can be a way for a cat to warn another cat to back off and not come any closer.

• Unfamiliarity: Cats may hiss at each other when they are unfamiliar with each other.

• Stressed out: Cats may hiss when they are stressed out, anxious, or uncomfortable.

• Rough play: Hissing can also be a sign of rough play between cats.

• Establishing dominance: Sometimes cats hiss at other adult cats to show dominance.

It is important to note that hissing is often a signal that the cat wants to avoid a physical confrontation, and the cat that hisses regularly is almost always the victim or the one being chased or antagonized. If you are introducing a new cat to your household, some hissing when they see each other is normal, and you should not be alarmed. However, if the hissing does not die down, you may need to separate them. If your cat is hissing at you, it could be a sign of fear, anxiety, or pain, and you should give them space and try to identify the cause of their discomfort.