Explanation:

 Ghoroud :
When Sand Dunes gather in a large group covering maybe hundreds or thousands kilometers, they're are called "Ghoroud" in Egyptian Western desert. 

"Ghoroud" is not likely to be Arabic (none is called so in Arabia or Eastern desert), it could be ancient Egyptian name of dunes , or maybe Berber too. Ghoroud is the word used for dunes in Egyptian Sahara. Ghard seems to be a singular form of Ghoroud and is used interchangeably (like water and waters).