A hoverbus was a vehicle similar to a hovercar but larger in size and capable of carrying more people.
While entering the Starfleet Training Center, Recruit James T. Kirk observed two white-and-blue Starfleet buses hovering near the main gate to the facility. (TOS novel: Academy: Collision Course)
In 2381, a hoverbus carrying Professor Vard and his students crashed for no reason but the passengers all mysteriously appeared in an alley, unharmed. (DTI novel: Watching the Clock)