Definition IGS: Interactive Geometry Software
Explanation: Interactive geometry software (IGS) are computer programs which allow one to create and then manipulate geometric constructions, primary in plane geometry. One starts construction by putting a few points and using them to define new objects (lines, circles, other points, etc). After some construction is done, one can move the points one starts with and see how the construction changes.
Other definitions in programming such as IGS: Interactive Geometry Software in Dictionary I.