lifer
/ˈlaɪfə(r)/noun
1
- informal a person serving a life sentence〈非正式〉无期徒刑犯。
2
- N. Amer. a person who spends their life in a particular career, especially in one of the armed forces〈北美〉终生从事某一职业的人（尤指终身职业军人）。