Young buxom wenches, ripe and prone to venery, but who have not lost their virginity, which the upright man claims by virtue of his prerogative; after which they become free for any of the fraternity. Also a common strumpet. Cant.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Degen * DemureNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes