red box

plural red boxes

1. A phreaking device that generates tones to simulate the insertion of coins into a payphone, thus enabling the user to make illegitimate free calls.
2. UKgovernmentA secure briefcase-like box used by ministers in the British government to carry their documents.

   Downing Street has rejected suggestions that David Cameron might have caused a security breach by briefly leaving his official ministerial red box unaccompanied on the table of a train carriage.

   2013 September 9, Ben Quinn, “No 10 denies David Cameron red box security breach”, in The Guardian

   Synonyms: ministerial box

3. USgovernmentA safe located at a nuclear installation containing launch codes.
4. USinformalclimatologyA "tornado watch" notification, indicating that conditions might lead to a tornado though none has yet been sighted.

   See also: severe thunderstorm watch