blue box
noun
RareNot in standard dictionaries
1
A blue container used for the collection of household waste (such as tin cans and newspapers) for recycling by a municipal authority.
2
An electronic device used to bypass payment on a tone pulse telephone system.
3
A "tornado watch" notification category.
4
Ellipsis of USPS blue box.
5
Used other than figuratively or idiomatically: see blue, box.
#informal