Real Dictionary

concentration camp
a prison camp in which political dissidents, members of minority ethnic groups, etc. are confined
countable noun: A concentration camp is a prison in which large numbers of ordinary people are kept in very bad conditions, usually during a war.
noun: a guarded compound for the detention or imprisonment of aliens, members of ethnic minorities, political opponents, etc., esp. any of the camps established by the Nazis prior to and during World War II for the confinement and persecution of prisoners
noun: a guarded prison camp in which nonmilitary prisoners are held, esp one of those run by Nazi Germany in which millions were exterminated