What does it mean when a cat's tail vibrates? A cat's tail is a powerful form of communication that reveals its emotions and intentions. When the tail is erect and twitching, the cat is usually excited or happy, while a straight up she always vibrates her tail at this exact spot very.. confused?? anyone else experienced this? : r cats What is she trying to tell me? Vibrating tail??? : r CATHELP It looks like they are vibrating. When a cat's tail shoots straight up and quivers or rattles at the tip, it is the highest form of excitement they can show. It's a Cat tail signs: What your cat's tail tells you