A hovercar was a type of vehicle capable of hovering above ground rather than travelling on it. They were used by various races and cultures, including the United Federation of Planets and the Romulan Star Empire.
A Romulan hovercar in 2266.
In 2266, Commander Keras and Subcommander Decius took a Romulan hovercar from the Romulan Imperial Palace to a spaceport where they could be transported to the ChR Gal Gath'thong. (TOS comic: "Alien Spotlight: Romulans")
When they were on Risa in 2366, Gariff Lucsly informed Marion Dulmur they would have to hike to their destination, Dulmur asked if they could just rent a hovercar. (DTI novel: Watching the Clock)
Hovercars on Daborat V were able to defy gravity by using antigrav skids. (DS9 novel: The Heart of the Warrior)