( revolving doors)
1.
Some large buildings have revolving doors instead of an ordinary door. They consist of four glass doors which turn together in a circle around a vertical post.
As he went through the revolving doors he felt his courage deserting him.
N-COUNT : usu pl
2.
When you talk about a revolving door , you mean a situation in which the employees or owners of an organization keep changing.
They have accepted an offer from another firm with a busy revolving door.
N-COUNT : usu sing [ disapproval ]