1) German geological term 
A Dreikanter is a type of ventifact that typically forms in desert or periglacial environments due to the abrasive action of blowing sand. Dreikanters exhibit a characteristic three-faced pyramidal shape. The word Dreikanter is a German word meaning `three-edged.` A dreikanter is not to be confused with a zweikanter, which has only two sides, or.....
three-faced pebble worn by wind
(from the article `ventifact`) ...wind direction. As one surface is cut, the stone may become out of balance and may turn to expose another surface to the wind. A ventifact that ...
a pebble or boulder having three faces formed by the action of windblown sand.