pure and chaste. (Often used ironically. *Also: as ~.) Jill: Sue must have gone to bed with every man in town. Jane: And I always thought she was as pure as the driven snow.Robert was notoriously promiscuous, but tried to convince all his girlfriends that he was pure as the driven snow.
Morally unsullied, chaste, as in She's just sixteen and pure as the driven snow. This simile dates from the late 1500s, although driven, which means "carried by the wind into drifts," was occasionally omitted. It is heard less often today.