black bag
US informal (now chiefly historical )
adjective
Designating a covert intelligence operation carried out especially by the Federal Bureau of Investigation, involving illegal entry into premises; especially in black bag job.
- Such operations were declared to be unconstitutional in the United States in the early 1970s..
Origin
1960s; earliest use found in The Los Angeles Times. From the black bag in which equipment required for such an operation was typically carried.