An interruption of a radio, telegraph, or telephone communication, as for sending in the opposite direction.

1. To interrupt processing by a computer, usually by depressing a key.

2. A place in a file of records where one or more of the values in the records change.

1. A fault in a circuit.

2. The minimum distance in a circuit-opening device between the stationary and movable contacts when these contacts are in the open position.

A reflected radar pulse which appears on a radarscope as a line perpendicular to the base line.

A significant variation of topography, such as a deep valley.

See <<knickpoint>>

1. A sudden change in the weather; usually applied to the end of an extended period of unusually hot, cold, wet, or dry weather.

2. A hole or gap in a layer of clouds.

1. A plane of discontinuity in the coal seam such as a slip, fracture, or cleat; the surfaces are in contact or slightly separated.

2. A fracture or crack in the roof beds as a result of mining operations.