Anisotropy

Anisotropy (pronounced with stress on the fourth syllable: ) is the property of being directionally dependent, as opposed to Isotropy, which means homogeneity in all directions. In GIS it is a property of a spatial process or data in which spatial dependence (autocorrelation) changes with both the distance and the direction between two locations.

Computer graphics
In the field of computer graphics, an anisotropic surface will change in appearance as it is rotated about its geometric normal, as is the case with velvet.

Anisotropic filtering (AF) is a method of enhancing the image quality of textures on surfaces that are far away and steeply angled with respect to the point of view. Older techniques, such as bilinear and trilinear filtering don't take account of the angle a surface is viewed from, which can result in Aliasing or blurring of textures. By reducing detail in one direction more than another, these effects can be reduced.

Real World Imagery
Images of a gravity-bound or man-made environment are particularly anisotropic in the orientation domain, with relatively more image structure located at orientations parallel with or orthogonal to the direction of gravity (vertical and horizontal).