zastruga

from The Century Dictionary.

• noun One of a series of ridges, with corresponding depressions, rising in wave-like succession above the general level of the snow when this has been blown across by a long-continued wind.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Any of a series of long, wavelike ridges or grooves formed on a snow surface by the wind, especially in polar plains.