From Essential Scrum by Kenneth S. Rubin:
Idle work is work that we want to do (such as building or testing something) but can’t do because something is preventing us. […] Many product development organizations focus more on eliminating the waste of idle workers than on the waste of idle work. […] In Scrum, we are acutely aware that finding the bottlenecks in the flow of work and focusing our efforts on eliminating them is a far more economically sensible activity than trying to keep everyone 100% busy.
