longboat n : the largest boat carried by a merchant sailing vessel
In the days of sailing ships, a vessel would carry several boats for various uses. One would be a longboat, an open, primarily rowing, boat with eight or ten oarsmen, two per thwart. In other words the longboat was double banked: its rowing benches were designed to accommodate two men. Unlike the dinghy or the cutter, the longboat would have fairly fine lines aft to permit its use in steep waves such as surf or wind against tide where need be.
It had the double-banked arrangement in common with the cutter. This was possible as it had a beam similar to a cutter's but broader than that of a gig, which was single banked. The longboat was generally more seaworthy than the cutter which had a fuller stern for such load-carrying work as laying out an anchor and cable. In a seaway or surf therefore, the cutter was more prone to broaching to.
The Oxford English Dictionary notices uses of the word from 1515 to 1867. In later years, particularly in the Royal Navy, the longboat tended to be replaced by the whaler. The cutter was still in use in the 1950s but had been largely replaced by the 32 foot and 25 foot motor cutters.
Like other ships' boats, the longboat could be rigged for sailing but was primarily a pulling boat.
In some places such as Tristan da Cunha and Pitcairn Island the surf boats are known as longboats; perhaps because the settlers who introduced them were European seamen. The Tristan da Cunha boats are single banked.
The French link is to Chaloupe, which in this context is a cutter.
longboat in German: Beiboot
longboat in French: Chaloupe
longboat in Portuguese: Chalupa
longboat in Simple English: Longboat