concentration camp

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A camp where persons are confined, usually without hearings and typically under harsh conditions, often as a result of their membership in a group the government has identified as suspect.
• noun A place or situation characterized by extremely harsh conditions.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A camp where large numbers of persons—such as political prisoners, prisoners of war, refugees—are detained for the purpose of concentrating them in one place.
• noun A camp or premises in which persons considered to be undesirable by those who control it are hidden away, mistreated, and even killed.
• noun A situation wherein crowding and extremely harsh conditions take place.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a penal camp where political prisoners or prisoners of war are confined (usually under harsh conditions)
• noun a situation characterized by crowding and extremely harsh conditions