The term "revolving door" refers to:
The relationship between lobbyists and interest groups in which there is a constant turnover in the lobbyists hired by interest groups.
The constant visits by lobbyists to legislators in Congress.
The relationship between judges who become lobbyists and lobbyists who become judges.
The constant hiring of former federal government officials as lobbyists for interest groups.
The high turnover rate of members of Congress (incumbents failing to get reelected).