secret police

English Thesaurus

1. a police force that operates in secrecy (usually against persons suspected of treason or sedition) (noun.group)

hypernym	:	constabulary, law, police, police force,
definition	:	the force of policemen and officers (noun.group)

hyponym	:	gestapo,
definition	:	the secret state police in Nazi Germany; known for its terrorist methods (noun.group)