Term used, originally by the British police with reference to the IRA, to describe terrorists with no previously known connections to terrorism.
From the Observer: "They even won over former Irish soldiers, at least five of whom are now in jail. Many of those it recruited are so-called 'lilywhites', with no previous convictions. They are hard to trace and even harder to catch. But they are deadly and effective."
by ffub July 14, 2005