What does it mean if my cat's tail is vibrating?

[tabbytom]

The only time my boy's tail vibrate or quivers is when he is peeing. Guess it was a relieve

 

[KarenKat]

I am sorry about Gohan's accident. Has the vet said if he will cmpletely recover his tail movements?

Thanks, he’s doing much better now. The vet said it was uncertain, only time will tell. But over the last month it’s moved from totally limp to him having most movement back with the exception of the top third. The tip will twitch and curl from time to time so we are hopeful he will be mostly back to normal.

 

[losna]

Sinbad does this when I look at him and say his name. He sort of shivers, his ears pop up, his tail shoots into the air, vibrates and becomes SUPER PUFFY. Often he'll trill/chirp too.