When a cat hisses, it is usually a sign that the cat is feeling anxious, frightened, or agitated. However, there are other reasons why a cat will hiss, such as pain, unfamiliarity, stress, rough play, or annoyance. Hissing is an expression of discomfort, fear, or stress. Here are some of the reasons why a cat might hiss:

• Warning shots: Cats hiss to warn someone or something to back away. Its a defensive sound, alongside growling, yowling, and spitting.
• Pain: Cats will hiss if they are in pain.
• Unfamiliarity: Cats are sometimes upset by new or unfamiliar things, including people, objects, or changes in environment. This fear or discomfort can prompt hissing at what might appear to be nothing.
• Stressed out: Most of the time a cat will hiss because they are feeling nervous or anxious about something.
• Rough play: Overstimulation is the most common reason for a cat to hiss at their pet parent. Depending on your cat’s threshold, a few minutes of petting or a rough play session could be enough to cause your cat to hiss.
• You’re bugging them: Cats will hiss if they are annoyed or feel like they are being bothered.

It is important to note that hissing is often a signal that the cat wants to avoid a physical confrontation. When a cat hisses, it is best to back away and give them space.