blue box

Short definition from Wiktionary

Noun

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