Film adaptation: To what extent is the phrase ‘faithful adaptation’ a contradiction in terms?

Well, I don't know any factual information, but my opinion would be that it depends how closely the movie followed the book. For instance, Along Came a Spider and The Bone Collector were both fairly faithful, with only minor details changed or deleted, but The Lightning Thief had a bit at the end that didn't happen until the middle of book two. I am trying to say, if the movie doesn't drastically alter the timeline, or the storyline, then it should be called "faithful."