Inveterate (adjective)

1. Having a particular habit, activity, or interest that is long-established and unlikely to change.
2. Deep-rooted and ingrained; ingrained, long-standing, and unlikely to change.

Origin:

Early 17th century from latin inveteratus, from in- "in" + veteranus "old, experienced".

Examples:

1. He was an inveterate smoker and couldn't quit the habit.
2. She was an inveterate gambler and couldn't resist the urge to gamble.
3. He was an inveterate traveler and couldn't stay in one place for long.
4. She was an inveterate reader and spent most of her free time with a book.
5. He is an inveterate liar and can't tell the truth.