black bag

Short definition from Wiktionary

Adjective

1. 1
   Alternative spelling of black-bag.
2. 2
   Involving sophisticated clandestine methods for gaining unauthorized entry and obtaining information.

Noun

1. 1
   A black plastic sack produced for the disposal of household waste.
2. 2
   The pouch or case traditionally carried by medical doctors, especially when making house calls, and containing medical instruments and supplies.
3. 3
   A pouch or case containing burglary tools.
4. 4
   Synonym of football (“the leather briefcase containing classified nuclear war plans which is always near the US President”)

Verb

1. 1
   To break in to a place without authorization as part of a clandestine operation.
2. 2
   To kidnap in order to make someone disappear (as opposed to kidnapping for ransom).