If you're an inveterate doodler, all your notebooks are covered with drawings. If you're an inveterate golf player, you probably get twitchy if you haven't been out on a course in a week.
Inveterate comes from the Latin root for “old,” and it describes old habits. In Middle English the word was associated with chronic disease. Now it simply refers to something that is a signature habit with a person. If you’ve loved books ever since you were a toddler, and you regularly check out big stacks from the library, you’re an inveterate reader. And if you're an inveterate nail-biter, nothing can cure you of the habit.