If you were to ask what is human language, it would be the superset of sign language, spoken language, body language, etc. If you take that kind of approach when deciphering the language of cats, just as convnets can decipher the hidden logic of recognising faces, I'd imagine a rudimentary form would be a mixture of visual and auditory signals designed to "trick" the cat into responding.
Cats are smart enough to communicate with humans, I have no doubt of that. N=2, but once I had a cat that woke me up at night to point out a possum had entered the house and was hiding under a piece of furniture, and once I had one which (different house) gestured me to follow him in the chase after shooing away the intruder cat that kept stealing its food.
