bore

Bore is a term with several related senses. In engineering, it denotes the interior diameter of a hollow cylinder, such as a pipe or gun barrel. The hole produced by drilling is also called a bore, and the process is boring. Bore diameter is a key specification affecting performance and fit in machining, piping, and firearms.

In firearms, the bore is the barrel's interior width; caliber describes the size of the bullet designed to fit it. In machining, boring enlarges or finishes a hole to a precise size, often using a boring tool, boring head, or reamers to improve roundness and surface finish. A bore gauge measures bores.

As a slang noun, a bore is a dull or tedious person.

In hydrology, a tidal bore is a surge of tidal water that travels upstream in a river, forming a rising wave. Well-known examples include the Severn bore in the United Kingdom and the Qiantang bore in China.

Other uses include the verb “to bore,” meaning to make a hole or to drill through something, and the noun form “borehole” for the resulting channel. In engineering contexts, bore diameters and tolerances are important for ensuring proper fit and function.