Breadcrumb Home > Dictionary > Index B blue box: Meaning and Definition of Find definitions for: blue' box' Pronunciation: [key] an electronic device used by phone phreaks to send out signals that unlock long-distance telephone circuits. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. bluebottle fly blue-breasted quail ✖ Related Content Daily Word Quiz: musth Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language