One whose scrotum is so relaxed as to be longer than his penis, i.e. whose shot pouch is longer that the barrel of his piece.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
Rank Rider * RantipoleNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes