The phrase "dirty work" refers to any unpleasant, difficult or dangerous task that needs to be done. It is often associated with jobs that involve physical labor, such as cleaning up messes, repairing things, or handling hazardous materials. The term can also refer to tasks that are morally questionable or require deceitful behavior, such as spying or undercover work. In general, the phrase "dirty work" is used to describe any task that is unpleasant, difficult, and requires effort or courage to complete.