Definition
A person who is habitually engaged in a particular activity, often something undesirable, and is unlikely to change their behavior; for example, a liar or a gambler.
老毛病（指很难改掉的坏习惯）
He's an inveterate smoker; he feels unwell if he doesn't smoke for a day.
他是个老烟枪，如果一天不抽烟就会觉得不舒服。
She is an inveterate latecomer; no matter what time we agree, she always arrives late.
她是个迟到大王，无论我们约什么时间，她总是迟到。
Despite several attempts to quit, he remains an inveterate gambler.
尽管多次尝试戒掉，他仍然是个老赌徒。