Slide Rule

a thin flat calculating device consisting of a fixed outer piece and a movable middle piece Both pieces are graduated in such a way as by a logarithmic scale that multiplication division and other mathematical functions of an input variable may be rapidly determined by movement of the middle pieces to a location on one scale corresponding to the input value and reading off the result on another scale A movable window with a hairline assists in alignment of the scales This device has been largely superseded by the electronic calculator which has a greater precision than the slide rule Also called colloquially slipstick