Refers to the differences in physical properties of rocks as related to the directional characteristic; for example, strength or drillability may be different when measured in different directions through the rock. (Bul D20)
The Mudblogger (Oilfield, Energy and Related Photographs), Oil Field Glossary, TX, USA 2014. http://mudblogger.com/oilfield-glossary/, (Oil - Amer) {777}