outbox /ˈaʊtbɒks/noun 2/aʊtˈbɒks/ verb 1forms 3 noun2 •A box holding papers to be transmitted to others, usually by mail.Rabin tossed the orders in his outbox, dipped the brush back in the small bottle, and continued to apply more solvent […] — 2013 •An electronic folder serving the same purpose, for electronic mail. outbox /aʊtˈbɒks/ verb1 •To box better than. formsoutboxed · outboxing · outboxes