Pure as the driven snow 意為「(道德、人品等的) 純潔無瑕的，純真無邪的，玉潔冰清的」，其中 driven snow 指的是「(沒有被踩踏過的) 積雪」。這個慣用語可追溯到 1800 年代，但它的根源較此更早許多。
與其他許多使用 like 或 as 來做兩件事物之比較的慣用語一樣，(be as) pure as the driven snow 也是明喻 (simile) 的運用。這個慣用語於十八和十九世紀之交開始使用，但它最可能源自莎士比亞的戲劇。在《哈姆雷特》(Hamlet) 中，有句話說：”…be thou as chaste as ice, as pure as snow…”。
例句：
- If you expect teenagers to remain pure as the driven snow, you’ve got another think coming. (如果你以為青少年都會保持純真無邪，那你就想錯了)
- Teresa would never cheat on an exam. She’s pure as the driven snow. (泰瑞莎考試從不作弊。她純潔無瑕)
- She’s tall, blonde, just sixteen and pure as the driven snow. (她只有 16 歲，身材高挑，白膚金髮碧眼，玉潔冰清)
- How dare Simon criticize his wife for having an affair? He’s not exactly as pure as the driven snow himself. (賽蒙怎麼敢指責他太太有外遇？他自己也不是純潔無瑕的)