Bullnose is a term used in building construction for rounded convex trim, particularly in ceramic tile.

Uses

Bullnose trim is used to provide a smooth, rounded edge for countertops, stair steps, building corners, Verandahs

Verandah

A veranda or verandah is a roofed opened gallery or porch. It is also described as an open pillared gallery, generally roofed, built around a central structure...

 or other construction.

When referring to bullnose, it is sometimes modified by adding the word quarter or half. In the illustration, one piece of quarter-bullnose tile is juxtaposed with a plain piece of tile, to create a finished look - note that the top trim strip shows a quarter-bullnose on two of its sides.

However, when referring to counter tops (such as a granite counter top in a kitchen) which extends beyond the edge of the underlying cabinetry, either a quarter-bullnose or half-bullnose edge may be used. A half-bullnose can be constructed by bonding two sections with quarter-bullnose, effectively creating a 180-degree curve, in order to create a more finished appearance. This would effectively double the thickness of that portion which extends beyond the cabinetry.

Bullnose is used in highway construction in North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 to buffer and protect the end of the Crash barrier or Jersey Barrier

Jersey barrier

A Jersey barrier or Jersey wall is a modular concrete barrier employed to separate lanes of traffic. It is designed to both minimize vehicle damage in cases of incidental contact while still preventing crossover in the case of head-on accidents....

at an entrance and exit ramps.