Definition of blue box:
(n) :
(chiefly British and Canada) A blue container used for the collection of household waste (such as tin cans and newspapers) for recycling by a municipal authority.
(n) :
(informal, US, meteorology) A "tornado watch" notification category.
(n) :
(historical, telephony) An electronic device used to bypass payment on a tone pulse telephone system.
(n) :
Used other than figuratively or idiomatically: see blue, box.