“Anisotropy” means that the properties of a material depend on the direction in which the force is applied.
The 3D printing process tends by nature to build up a weakness along the Z axis because the connections between the layers are not so strong.
This peculiarity of the 3D printing processes is known to the manufacturers and so the strength along the printing axis is also indicated as a reduced value in many data sheets of materials for e.g. SLS materials.
If one is dependent on the strength in a part, it is important that one is aware of this property.
This also means that the part is weakest along the printing axis and usually breaks there.
This can be counteracted by placing the component in the slicer in such a way that the greatest force is not applied to the Z axis of the printer.
However, this often means that the component is rotated by 30° or 45° along the X or Y axis, for example, and you suddenly have to print support for a part that would not actually need it.
For more information on strength in 3D printing, see also: Was ist der Einfluss der Fülldichte, Schichtdicke und Füllmuster bei meinen 3D-Drucken [German] or Influence of Infill, Layer Height and Infill Pattern [English]