ShearingTransform

ShearingTransform[θ, v, n] gives a TransformationFunction that represents a shear by θ radians along the direction of the vector v, normal to the vector n, keeping the origin fixed.

ShearingTransform[θ, v, n, p] gives a shear that keeps the point p fixed, rather than the origin.

Examples

Apply a 2D shear:

ShearingTransform[0.5, {1, 0}, {0, 1}][{1, 1}]
(* {1.54931, 1} *)

Shear a rectangle:

Graphics[{
  EdgeForm[Black], 
  GeometricTransformation[Rectangle[], ShearingTransform[0.3, {1, 0}, {0, 1}]]
}]

Please visit the official Wolfram Language Reference for more details.