The Collaborative International Dictionary
packet \pack"et\ (p[a^]k"[e^]t), n. [F. paquet, dim. fr. LL. paccus, from the same source as E. pack. See Pack.]
A small pack or package; a little bundle or parcel; as, a packet of letters.
--Shak.-
Originally, a vessel employed by government to convey dispatches or mails; hence, a vessel employed in conveying dispatches, mails, passengers, and goods, and having fixed days of sailing; a mail boat.
Packet boat, Packet ship, or Packet vessel. See Packet, n., 2.
Packet day, the day for mailing letters to go by packet; or the sailing day.
Packet note or Packet post. See under Paper.
WordNet
Wikipedia
Packet boats were small boats designed for domestic mail, passenger, and freight transportation in European countries and their colonies, including North American rivers and canals. They were used extensively during the 18th and 19th centuries and featured regularly scheduled service.
When such ships were put into use in the 18th century on the Atlantic Ocean between Great Britain and its colonies, the services were called the packet trade.
Usage examples of "packet boat".
It was a New Orleans packet boat, Marsh saw as they got near, a medium-sized side-wheeler named the H.
The packet boat is two degrees off to starboard and, at our present speed, forty-one minutes ahead of us.
Through the window he could see the packet boat loading by the quay.
In any event, Charles was with Abigail when she arrived by packet boat in New York at the start of summer, and life for the Vice President took a decided turn for the better.
I did try to make him stay, but he was bound for New Bern by the packet boat, and couldna bide.
For the last few days she had looked over this salvaged starship-once a Buyur packet boat, according to Chuchki.
Nor was there a packet boat or frigate waiting for him there, as he might have expected, with word from Graves.