1. an entrance door for excluding drafts from the interior of a building, usually consisting of four rigid leaves set in the form of a cross and rotating about a central, vertical pivot in the doorway.
2. Informal. a. a company, institution, or organization with a high turnover of personnel or members.
b. a legal, medical, or other system or agency that discharges criminals, patients, etc., in the shortest possible time and without adequate attention or consideration.