“Greedy work” refers to jobs in which earnings are convex in hours - meaning that working longer, more continuous, and less flexible hours is rewarded disproportionately rather than proportionally. {Summarized by the robot.}
And, from Claudia Goldin:
Greedy work can be defined as a job that pays disproportionately more on a per-hour basis when someone works a greater number of hours or has less control over those hours. It could be a rush job, a demanding client who calls at 11 PM, or a supervisor who asks that the worker give up a vacation day for the project. The firm has deemed the additional payment worth it to have the work done over more hours, at a particular time, or during odd hours. The other critical aspect is that the worker agrees to do it at that wage. Supply and demand, all over again.