An Akaali clipper ship.
Clipper ships were a type of multiple-masted sailing ships used on Earth beginning with the 19th century.
When Data met Guinan in San Francisco in the year 1893 and told her he was from the Enterprise she asked whether that was a clipper ship, not knowing about her future stay on the USS Enterprise-D, the ship Data was referring to. (TNG: "Time's Arrow")
The Akaali built similar three-masted clipper ships as the crew of the Enterprise was able to observe from orbit when visiting the Akaali homeworld in 2151. (ENT: "Civilization")