Cats hiss and spit to signal both offensive and defensive aggression. Purring usually signals contentment, reassurance or greeting, but cats also purr to comfort themselves when stressed, according to International Cat Care.
Cats communicate through a wide range of behaviors. They trill or chirp in greeting and meow to signal friendship or gain attention. Cats also use visual signals involving the eyes, ears, tail and general posture. An arched back and puffed-out tail signal defensive aggression, while forward-tipped ears and a tail held high indicate friendly intentions. Tactile communication includes touching and rubbing, mutual grooming, nose touching and sharing of rest areas. Cats communicate through smell as well, marking territories with urine, feces and scent glands on the head and feet.