This is an angry cat that could be getting ready to attack. It's best to back off until he calms down. This is an aroused cat. If lowered it can mean fear. It up, it can mean an aggressive cat.
Cats bristle their tails and the fur on their bodies when aroused.
This makes them look larger than they are in an attempt to intimidate whatever is worrying them. Tail held straight up and quivering as the cat is backed up against a vertical object like a bush or tree. This is a cat that is marking its territory with urine. All rights reserved.