- a public box in which mail is placed for pickup and delivery by the post office.
- a private box, as at a home, into which mail is delivered by the mail carrier.
- Computers. a file for storing electronic mail.
- mainly US and Canadian
- a slot, usually covered with a hinged flap, through which letters, etc are delivered to a building
- a private box into which letters, etc, are deliveredAlso called (in Britain and certain other countries): letter box
- mainly US and Canadian a public box into which letters, etc, are put for collection and deliveryAlso called (in Britain and certain other countries): postbox
- (on a computer) the directory in which e-mail messages are stored; also used of the icon that can be clicked to provide access to e-mails
n.also mail-box, 1797, “box for mailbags on a coach,” from mail (n.1) + box (n.1). Meaning “letterbox” is from 1853, American English.