Someone with a big ol' dick. Great big wang. Humongous todger. A sizeable cock. An enormous meat stick. A hugewilly, or Gigantic pipe. The most grand of all yoghurt slings. A large penis.
Gee, that's rather a monumental Joystick between your legs, you absolute Gawen.
This is made up of fivewords: give a fuck, me? NOT!
And is used when somebody is trying to get your attention on a subject you don't really, ummm, give a fuck about.
Use it in similar circumstances, with emphasis on whichever syllable you want to create the right kind of impression on whoever is trying to get your attention.
Edwinus: So, are you grateful that Jesus died for your sins?
Zippy: Gafmenot, moron, gaf me fucking not.