The word “highball” is used in bouldering and in no other discipline of rock climbing. It means a taller than average boulder problem, especially one where the consequences of falling are not insignificant. You don’t want to fall from near the top of a highball.
This video embedded below gives a good idea of what a highball is:
And this video, while a bit drawn out and melodramatic, shows French climber Romain Desgranges’s efforts to climb the ten classic highballs of southern California’s Joshua Tree National Park: