In order to keep a road or rail line straight and/or flat, and where the comparative cost or practicality of alternate solutions (such as diversion) is too prohibitive, a piece of a hill or mountain is cut out to make way for it. Contrary to the general meaning of cutting, a cutting in construction is usually blasted out with carefully-placed explosives. The cutting may only be on one side of a slope, or directly through the middle or top of a hill. Generally, a cutting is open at the top (otherwise it is a tunnel). Cutting is the separation of a physical object, or a portion of a physical object, into two portions, through the application of an acutely directed force. ... A disused railway tunnel now converted to pedestrian and bicycle use, near Houyet, Belgium A tunnel is an underground passage. ...

The word is also used in the same sense in mining, as in open-cut mine.