zastrugi

sas·tru·ga

(să-stro͞o′gə, săs′trə-, sä′strə-) also zas·tru·ga (ză-stro͞o′gə, zä-)
n. pl. sas·tru·gi (-gē) also zas·tru·gi
A long wavelike ridge of snow, formed by the wind and found on the polar plains.

[Russian dialectal zastruga : za, beyond + struga, deep place into which one may fall; see sreu- in Indo-European roots.]