The growl is clearly warning sound. Cats growl at one another to say, "Back off before I have to use my claws rather than my voice!"

A cat can growl if it is angry, in pain, or being territorial. It implies unhappiness from annoyance, anger, aggression, or fear. It is a signal to back off. Growling can occur from a variety of triggers. Some cats can be food or toy aggressive and growl to show possession. If a cat is annoyed from physical contact, it may growl.