noun
wind blowing down from a mountain
A local wind that descends mountain slopes, often cold and strong; used in weather contexts and regional descriptions.
山おろしが吹いて、急に寒くなった。
A mountain wind blew down and it suddenly got cold.
颪 is the generic term for a wind blowing down a slope; 山おろし specifically refers to a mountain wind.
Compound of 山 (yama, 'mountain') and 颪 (oroshi, 'wind blowing down from mountains'). The kanji 颪 is a kokuji (Japanese-made character) combining 下 (down) and 風 (wind).