"Rent seeking" is a business taking steps in order to receive a monopoly. The term "rent" is used because economists use rent to refer to extra-competitive profits. Most often rent seeking means lobbying government for government-granted monopoly.

Rent seeking is economically inefficient because the firms seeking a monopoly will apply resources to things like taking congresspeople out to lunch instead of investing those resources into production or R&D.

At its worst, rent-seeking can deplete lots of resources, because multiple firms will be lobbying for the same monopoly. So, there is competition in who spends the most lobbying government.

As an example of the results of rent seeking, check out the Sonny Bono Copyright Extension Act.