ETYM Old Eng. faut, faute, French faute (cf. Italian, Spanish, and Portu. falta), from a verb meaning to want, fail, freq., from Latin fallere to deceive. Related to Fail, Default.
1. Responsibility for a bad situation or event.
2. A serve that lands outside the prescribed area.
3. (Geology) A fracture in the earth's crust with displacement of one side with respect to the other; SYN. geological fault, fault line, fracture, break.

1. To charge with a fault; to accuse; to find fault with; to blame.
2. To interrupt the continuity of (rock strata) by displacement along a plane of fracture; -- chiefly used in the p.p..

1. A physical defect, such as a loose connection, that prevents a system or device from operating as it should.
2. A programming error that can cause the software to fail.
3. As page fault, an attempt to access a page of virtual memory that is not mapped to a physical address. See also page fault.

In geology, a fracture in the Earth's crust along which the two sides have moved as a result of differing strains in the adjacent rock bodies. Displacement of rock masses horizontally or vertically along a fault may be microscopic, or it may be massive, causing major earthquakes.
If the movement has a major vertical component, the fault is termed a normal fault, where rocks on each side have moved apart, or a reverse fault, where one side has overridden the other (a low angle reverse fault is called a thrust). A lateral fault, or tear fault, occurs where the relative movement is sideways. A particular kind of fault found only in ocean ridges is the transform fault (a term coined by Canadian geophysicist John Tuzo Wilson 1965). On a map an ocean ridge has a stepped appearance. The ridge crest is broken into sections, each section offset from the next. Between each section of the ridge crest the newly generated plates are moving past one another, forming a transform fault.
Faults produce lines of weakness that are often exploited by processes of weathering and erosion. Coastal caves and geos (narrow inlets) often form along faults and, on a larger scale, rivers may follow the line of a fault.