revolving door

noun

1. a door consisting of three to five upright panels hung on a central axle, and turned around by pushing on one of the panels: used to keep out drafts of air
2. anything like a revolving door, as
   1. something that leads back to a previous place or condition for some criminals, the justice system is a revolving door back to the streets
   2. a place or situation through which a stream of persons passes, as a job with a high turnover rate

adjective

1. designating or of the practice in which a former employee of a government department goes to work for a private company regulated by that department
2. having a high turnover of personnel, members, etc.: said of a company, organization, etc.