The phrase per diem means per day or by the day.. In terms of jobs, if the position itself is per diem it probably means that it is not steady work. Instead, they will, at best, be hiring you on days when they need you (sort of like substitute teaching would be).Per diem can also refer to payments that you get in addition to your regular pay.his means payment based on quantity of work done. Generally wages are paid per diem basis for temporary, short term asignments rather tah for regular long term jobs. flprof | College Teacher | (Level 1) eNoter. Posted on. (Answer #3). Per Diem can have a few meanings when it comes to employment.