As far as your cat is concerned, you’re another part of their territory, and rubbing their tail on you is an excellent way to let the world know.
In other cases, those tail slaps could be much more intentional and a swishing tail could be a sign of overstimulation in cats.
Sometimes, cats just do something because it’s fun. I don’t think cats enjoy hitting you with their tail (whether in your face or on the legs), but they probably love the feeling of slapping just about anything on their tail.
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