Capricious.

'Capricious. You're capricious. That means like a goat.'

'No it doesn't. Anyway, I'm not like a goat.'

'You are. You do things on a whim. Rash things, you get your head down and charge. That's like a goat, and that's capricious.'

'Will you get it into your head that I'm not like a goat.'

'You may not be Like a goat, but you certainly like them.'

'I don't like goats. Vicious things.'

'You've slept with a goat.'

'I've never slept with a goat. How dare you insinuate such things? You can get into severe trouble for doing things like that. Look what happened to Dumbledore's brother Aberforth. It's all in Hogwarts, A History.'

'Hermione. You have so slept with a goat, at least technically. I don't know how you passed Transfiguration. I'm an animagus.'