lifer

lifer /ˈlaɪfɚ/ noun
plural lifers
lifer
/ˈlaɪfɚ/
noun
plural lifers
Britannica Dictionary definition of LIFER
[count] informal
1 
US : a person who spends an entire career in the same job
2 
: a criminal who has been sentenced to spend the rest of his or her life in prison