or PACKET BOAT, a vessel appointed by the government to carry the mail of letter, packets, and expresses from one kingdom to another by sea in the most expeditious manner. Thus, the packet-boats, under the direction of the postmaster-general of Great Britain, carry the mails from Dover to Calais, from Falmouth to Lisbon, from Harwich to Helvoetsluys, and from Parkgate to Dublin. See POST.