man-month

noun1

1. •
   One person's working time for a month, or the equivalent, used as a measure of how much work or labor is required or consumed to perform some task.

   • In project management, there is always another dimbulb who will ask whether the relationship of man-months to calendar months is such that the schedule can be cut in half by doubling the headcount. The standard joke for disabusing this nonsense involves an expedited pregnancy lasting four and a half months instead of nine.