Full Definition of SLOPE. 1. : ground that forms a natural or artificial incline. 2. : upward or downward slant or inclination or degree of slant.3. 4. a: the tangent of the angle made by a straight line with the x-axis b: the slope of the line tangent to a plane curve at a point.ull Definition of SLOPE. 1. : ground that forms a natural or artificial incline. 2. : upward or downward slant or inclination or degree of slant.