"If I'm having lessons with you, I won't have to do Occlumency lessons with Snape, will I." ''Professor Snape, Harry — and no, you will not." "Good," said Harry in relief, "because they were a —" He stopped, careful not to say what he really thought.
"I think the word 'fiasco' would be a good one here," said Dumbledore, nodding.
In that excerpt, Dumbledore replaces a word Harry has not said with 'fiasco'. Not being a native speaker myself, however, I've been wondering: what's the word that Harry would have said, had he not considered it inappropriate?