South African slang (perhaps used elsewhere as well) to mean a person who has never taken marijuana.
"So I remain a dagga virgin. Any rooker will tell you that's a terrible thing to be, let alone confess to, when you've already reached your sixties, though I remain hopeful that our unconventional health minister Manto Tshabalala-Msimang will one day allow South Africans to take marijuana for medicinal purposes."
by David Hogg October 2, 2006